Image display device

ABSTRACT

A compact, lightweight, low cost image display device with high image quality and improved brightness are attained by a combination of a color separating means and color separating/combining means and color combinations means and two reflecting means and polarizing plate to change the polarization direction of the light and a polarized beam splitter on the optical axis of reflective liquid crystal display element.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a display device for projectingimages on a screen using light valve elements such as liquid crystalpanels or reflective liquid crystal elements and relates in particularfor example, to an image display device for liquid crystal projectordevices, reflective image display projector devices, liquid crystaltelevisions and projection type display devices, etc.

[0003] 2. Description of the Related Art

[0004] Projection type display devices such as liquid crystal projectorsare known in the related art as a means to irradiate light from a lightsource such as an incandescent bulb onto light valve elements such as aliquid crystal display panel for projecting an enlarged image.

[0005] In image display devices of this type, light from a light sourceis changed and adjusted for brightness and darkness on each pixel in thelight valve element and projected on a screen, etc. In twisted nematic(TN) type liquid crystal display devices constituting typical liquidcrystal display elements, two polarizing plates are each installed atmutually different 90 degree light polarization directions, in the frontand rear of the liquid crystal cell formed by injecting liquid crystalsbetween a pair of transparent substrates having a transparent electrodefilm, and by combining the effect from selecting polarized lightconstituents of the polarizing plate and rotation of the deflectionplane by the electro-optical effect of the liquid crystal, the permeablelight intensity of the input light is controlled and image informationis displayed. In recent years, rapid progress has been made in makingthese permeable or reflective image display elements themselves morecompact and improving performance such as resolution.

[0006] The advancements in making display devices using light valveelements such as image display elements more compact and having highperformance had led not just simply to making image displays with videosignals as in the related art, but proposal of technology for projectortype image display devices constituted by image output device forpersonal computers. Demands here stress compactness and obtaining abright image extending to all corners of the screen. However, projectortype image display devices of the related art have the drawbacks ofbeing large and that the image brightness ultimately obtained andperformance characteristics such as image quality are inadequate.

[0007] For example when making the overall liquid crystal display devicemore compact, an effective method is to make the light valve elements orin other words, the liquid crystal display elements themselves smaller.However, when the liquid crystal display elements are made smaller, thesurface area irradiated by the liquid crystal means becomes smaller.Consequently, the surface area struck by the lighting means for thetotal luminous flux intensity emitted by the light source become smallerso the problem occurs that the percentage of luminous flux intensity(hereafter light utilization efficiency) on the liquid crystal elementwas low to the total luminous flux intensity emitted by the lightsource. Another problem is that the sides of the screen are dark.Further, the liquid crystal display element can only utilize thepolarized light in one direction so that only approximately half of therandom polarized light emitted from the light source is utilized.Technology for an optical system to-beam random polarized light from alight source on a liquid crystal display element aligned in a one-waypolarization direction, is disclosed in Japanese Patent Laid-Open No.H4-63318 wherein a polarity converter element such as a polarized beamsplitter is utilized and random polarized light beamed from a lightsource is separated into P polarized light and S polarized light andcombined together using a prism.

[0008] The optical system of the related art utilizing the abovearrangement, and particularly a lighting system utilizing a reflectiveliquid crystal display device was configured so that the polarized beamsplitter and reflective liquid crystal display element were combined andthe light polarization direction converted and checked according to theexpressed tones and the on/off of the video, and the video laterprojected onto a screen by a projecting lens.

[0009] Due to the polarized beam splitter, the above configuration hadthe problems that irregularities occurred in the color and the contrastwas low.

[0010] In other words, changes occurred in the permeance rate of the Ppolarized light to the angle of the input light beam and the reflectionrate of the S polarized light so that irregularities occurred in thereflection rate and permeance rate of the polarized beam splitter to thespecified angle of the lighting system. These irregularities causeddeterioration in the quality of the image quality projected on thescreen.

[0011] The polarized beam splitter such as disclosed in Japanese PatentLaid-Open No. 09-054213 with the permeant material enclosing the PB filmwas comprised of glass material with an optical resilience coefficienthaving an absolute value within 1.5×10⁻⁸ cm2/N, so that thebirefringence (double refraction) was low and the contrast on the screenwas improved.

[0012] However, in this example of the related art, the weight of thepolarized beam splitter glass material itself was heavy (more than twicethe conventional weight) , the utilization level was preferably lowsince the cost was high. However, in typical optical systems other thanthe embodiment of this invention, three R G B reflective panels wereused and each required a polarized beam splitter so that noconsideration was given to reducing the size, the weight or the cost ofthe optical system.

[0013] Also, in optical systems utilizing reflective liquid crystaldisplay elements, the dichroic mirrors or dichroic prisms made with adichroic coating and utilized for color separation or combination,changed the direction of the light by means of polarizing the directionof the light when beaming light in a system for color separation andcombination. The characteristics are known to change due to thepolarization direction of light beamed onto the dichroic coating. Inother words, a difference in light wavelength bands occurs in lightseparated into P polarized light and S polarized light. Morespecifically, on a dichroic blue reflective surface, the half wavelengthof a P polarized light input beam is lower than an S polarized lightinput beam. In such a case, the beam input with S polarized light isseparated into permeable light and reflected light according to the Spolarized light half wavelength λs by the blue reflective coatingsurface. When the image information is white, the light is convertedinto P polarized light by the blue reflective liquid crystal displayelement, and the light beam input again onto the blue reflective coatingsurface. This time the beam input with P polarized light is separatedinto permeable light and reflected light according to the polarizedlight half wavelength λp. In this case, the half-wavelength portion thathas fallen low is not reflected back and is a permeable part of thewavelength band. The light on the permeating part of the wavelength bandcannot be utilized in the image display device so the lighthalf-wavelength differential is lost and the brightness diminishes andcolor performance deteriorates. The same effects occur on the redreflective surface.

[0014] Therefore the light that deviates from this wavelength bandcannot be utilized. The problem of lowering of the light utilizationefficiency and a deteriorated color performance therefore occur in theimage display device.

[0015] Contrast is an important performance characteristics in imagedisplay devices, and inserting a polarizing plate between both or eitherof the polarized beam splitter and lighting system, and polarized beamsplitter and projection lens is effective in improving contrast.However, in the related art, all the red, blue and green light permeatesthrough the polarizing plate creating the problem of a rise intemperature in the polarizing plate, a drop in contrast, and burns onthe polarizing plate.

[0016] Therefore, as can be seen from the above description, measuresmust be taken to reduce the size of the optical system and projectionimage display system itself as well as reduce weight and reduce costswhile maintaining the image quality and the brightness of the imagedisplay device.

SUMMARY OF THE INVENTION

[0017] Methods to reduce the size and weight of the device itself, andlower the cost while maintaining the brightness and image qualityperformance of the image display device are therefore a problem in theabove described technology of the related art. In other words, theoptical efficiency of the dichroic prism constituting the colorseparating/combining means and the polarized beam splitter must beimproved, and a method for inputting and outputting light to areflective panel contrived and respective effective placement contrivedin order to improve the image contrast and brightness, reduce the sizeof the device itself, reduce the weight and lower the cost.

[0018] In view of the above problems with the related art, it is anobject of the invention to provide image display technology that iscompact and inexpensive while maintaining brightness and high imagequality.

[0019] In order to achieve the above objects, an optical unit of animage display device of this invention is comprised of a reflectiveimage display element for forming an optical image according to a videosignal from the light beam output from the light source, and a lightingsystem to beam the light onto the reflective image display element andsynthesize the light reflected from the reflective image displayelement, wherein the image display device is further comprised of acolor separating means to separate the input light into a plurality oflight beams, and a color combining means and the color separating meansare installed along the optical axis of the light separated from thecolor separating means.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020]FIG. 1 is an overall plan view showing a first embodiment of aprojection type liquid crystal image display device of the invention.

[0021]FIG. 2 is an overall plan view showing a second embodiment of theprojection type liquid crystal image display device of the invention.

[0022]FIG. 3 is an overall plan view showing a third embodiment of theprojection type liquid crystal image display device of the invention.

[0023]FIG. 4 is an overall plan view showing a fourth embodiment of theprojection type liquid crystal image display device of the invention.

[0024]FIG. 5 is an overall plan view showing a fifth embodiment of theprojection type liquid crystal image display device of the invention.

[0025]FIG. 6 is an overall plan view showing a sixth embodiment of theprojection type liquid crystal image display device of the invention.

[0026]FIG. 7 is an overall plan view showing a seventh embodiment of theprojection type liquid crystal image display device of the invention.

[0027]FIG. 8 is an overall plan view showing an eighth embodiment of anoptical unit used in an image display device of the invention.

[0028]FIG. 9 is an overall plan view showing a ninth embodiment of theoptical unit used in the image display device of the invention.

[0029]FIG. 10 is an overall plan view showing a tenth embodiment of theoptical unit used in the image display device of the invention.

[0030]FIG. 11 is an overall plan view showing an eleventh embodiment ofthe optical unit used in the image display device of the invention.

[0031]FIG. 12 is an overall plan view showing a twelfth embodiment ofthe optical unit used in the image display device of the invention.

[0032]FIG. 13 is an overall plan view showing a thirteenth embodiment ofthe optical unit used in the image display device of the invention.

[0033]FIG. 14 is an overall plan view showing a fourteenth embodiment ofthe optical unit used in the image display device of the invention.

[0034]FIG. 15 is an overall plan view showing a fifteenth embodiment ofthe optical unit used in the image display device of the invention.

[0035]FIGS. 16A, 16B and 16C are drawings showing the permeance rate ofthe light.

[0036]FIGS. 17A, 17B, and 17C are cross sectional plan views showing theembodiment for installing the liquid crystal element on the polarizedbeam splitter.

[0037]FIGS. 18A and 18B are perspective views showing an embodiment ofthe polarized beam splitter and an assembly base piece.

[0038]FIG. 19 is a side view for describing the installation of a ¼wavelength plate.

[0039]FIG. 20 is an overall perspective view showing an embodiment ofthe image display device of the invention.

[0040]FIG. 21 is a perspective view showing another embodiment of anoptical system.

[0041]FIG. 22 is an overall perspective view showing another embodimentof the image display device of the invention.

[0042]FIG. 23 is a perspective view showing still another embodiment ofthe optical system.

[0043]FIG. 24 is an overall plan view showing a sixteenth embodiment ofthe projection type liquid crystal image display device of theinvention.

[0044]FIG. 25 is an overall plan view showing a seventeenth embodimentof the projection type liquid crystal image display device of theinvention.

[0045]FIG. 26 is an overall plan view showing an eighteenth embodimentof the projection type liquid crystal image display device of theinvention.

[0046]FIG. 27 is an overall plan view showing a nineteenth embodiment ofthe projection type liquid crystal image display device of theinvention.

[0047]FIG. 28 is an overall plan view showing a twentieth embodiment ofthe projection type liquid crystal image display device of theinvention.

[0048]FIG. 29 is an overall plan view showing a twenty-first embodimentof the projection type liquid crystal image display device of theinvention.

[0049]FIG. 30 is an overall plan view showing a twenty-second embodimentof the optical unit used in the image display device of the invention.

[0050]FIG. 31 is an overall plan view showing a twenty-third embodimentof the optical unit used in the image display device of the invention.

[0051]FIG. 32 is an overall plan view showing a twenty-fourth embodimentof the optical unit used in the image display device of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0052] The embodiments of the invention are hereafter described whilereferring to the accompanying drawings.

[0053] An overall plan view showing the first embodiment of theprojection is shown in FIG. 1. The embodiment in FIG. 1 shows threeplate type projection display devices utilizing a total of three platesfor the three primary colors R (red) , G (green) and B (blue)constituted by reflective liquid crystal elements 2 as the liquidcrystal light valves.

[0054] The projection display device in FIG. 1 contains a light source1. The light source 1 is a white color lamp such as an ultra highvoltage mercury lamp, metal halide lamp, xenon lamp, mercury xenon lampor halogen lamp, etc. The light source 1 contains at least onereflective mirror 5 having a circular or polygonal output beam apertureand the light output from the light source 1 passes through thereflective liquid crystal elements 2 constituting the liquid crystallight valves, progresses to the projection lens 3 and is projected ontothe screen 4.

[0055] The light emitted from the lamp of the light source 1 iscondensed by a reflector 5 having an elliptical surface, or a radialsurface or a non-spherical surface, and input to a first array lens 6comprised by a plurality of condensing lenses installed in the outputbeam aperture of this reflective mirror 5 and rectangular frame ofequivalent size, and the light beamed from the lamp unit is concentratedto form a plurality of secondary light source images on the first arraylens 6. The light passes through a second array lens 7 comprised by aplurality of condensing lenses installed in the vicinity of theplurality of above mentioned secondary light source images and furtherforming images of the lens images of first array lens 6 on a liquidcrystal display element 2. The emitted light beam is input to a row ofdiamond-shaped prisms of about half the size of each lens widthinstalled for an appropriate pitch laterally along the optical axis ofeach lens of the second array lens 7. A polarized beam splitter 8 filmhas been coated on the surface of these prisms and the input light isseparated into P polarized light and S polarized light by the polarizedbeam splitter 8. The P polarized light proceeds directly through theinterior of the polarized beam splitter 8 and is rotated 90 degrees anddeflected by the λ/2 wavelength polarizing plate 9 installed on theoutput beam surface of the prism, converted into S polarized light andoutput. The S polarized light on the other hand, is reflected by thepolarized beam splitter 8, and after being reflected once more along thebasic direction of the optical axis within the adjoining diamond-shapedprism, is output as S polarized light. The emitted light is input to acollimator lens 10.

[0056] In the projection type image display device using the reflectiveliquid crystal display elements of the related art, the polarized lightis reflected in only one direction due to the combination of input lightpolarizing plate and reflective liquid crystal display elements, so thatonly about half the reflected light amount is obtained. However, byusing the polarized beam splitter 8, a projection liquid crystal displaydevice 2 having twice the brightness of the related art cantheoretically be obtained by aligning along the direction of the randompolarized light emitted from the light source 1 and inputting the lighton the liquid crystal display element 2. Further, uniform quality can beobtained by overlapping the individual images of each lens cell of thearray lens 6 on the liquid crystal display element 2.

[0057] The collimator lens 10 is comprised of at least one or morelenses, has a positive refractive potential, and has the effect offurther concentrating the S polarized light. The light passing throughthis collimator lens 10 is deflected a specified 90 degrees by theoptical axis direction of the reflective mirrors 11 and 12. The lightthen passes through a condenser lens 30 and beams onto (irradiates onto)the three RGB reflective liquid crystal display elements 2R, 2G, 2B sothat light is separated into two portions, one of G (green) light andthe other R, B (red and blue) light by the color separating prisms (notshow in the drawing) or the color separating mirror 13, and input to therespective exclusive color polarized light separating/combining elementsconstituted by the polarized beam splitters 16G and 16RB. In otherwords, the G light is input to the G exclusive polarized beam splitter16G of this invention, and is then an S polarized light, so is reflectedto the reflective liquid crystal display element 2G and illuminates thepanel. Further, the B light and R light passes the B-R exclusivepolarizing plate 14, is input to the B-R exclusive beam splitter 16RB ofthis invention. Either the B light or the R light then passing throughthe designated wavelength converter element 17 that converts light onlyof that designated wavelength, is converted from S polarized light to Ppolarized light. The B light as P polarized light converted frompolarized light for example, passes through the R-B exclusive beamsplitter 16RB and illuminates the B exclusive reflective liquid crystaldisplay element 2B. The R light on the other hand, is S polarized lightso after being reflected by the R-B exclusive beam splitter 16RB isilluminated on the reflective liquid crystal display element 2B. Theabove description is of course only one example and the invention is notlimited by this example. A configuration may be utilized wherein the Rlight is for example converted into P polarized light, or the originalpolarized light of the illuminating system may be P polarized light, andone of the RGB colors may be converted into S polarized light, and theremaining two colors constitute P polarized light. A R-B exclusive inputpolarizing plate 14 and a G exclusive polarizing plate 15 are installedon the light incident side of the reflective liquid crystal displayelements 2R, 2G, 2B for each color, the polarization intensity of eachcolor enhanced, a polarizing plate 14 stuck to the glass and the colorpurity enhanced by coating a color alignment film on the reflectingside. Then, the polarized light is exclusively converted by thereflective liquid crystal display elements 2 for each color, and thelight then input again to the exclusive beam splitters 16G, 16RB, the Spolarized light reflected and the P polarized light permeates through.

[0058] A plurality of reflective liquid crystal display elements 2 areformed to correspond to the number of display pixels (for example, 1024horizontal pixels and 768 vertical pixels for each of the three colors,etc.) . The light polarization angle of the pixels matching the liquidcrystal display elements 2 changes according to an external drivesignal, and ultimately a light is output in the polarization directionof the input beam and an intersecting direction, and light matching thepolarized light direction is analyzed by the polarized beam splitter 2.The light intensity passing through the polarized beam splitter and theanalyzed light intensity are determined for light along the deflectionlight angle, by its relation with the polarization angle of thepolarized beam splitter 2. The image is in this way projected accordingto an externally input signal. At this time, the polarization directionis the same as the input light in the polarized light converter elementconstituted by the B exclusive beam splitter 16G and the R-B exclusivebeam splitter 16RB of this invention, when a black display is shown onthe reflective liquid crystal display elements 2R, 2G, 2B, and the lightreturns as is, along the light input path, to the light source side.However, the degree of deflection and extinction rate of the polarizedbeam splitter that constitute the light analyzing efficiency exert aminute effect on performance, and a slight leakage or disturbance in thepolarized light passes through the polarized beam splitter, passesthrough the color combining mirror 19 or the color combining prism andilluminates onto the projection lens 20 and appears as a minute amountof brightness on the screen during a dark display. A decline in thecontrast performance therefore occurs.

[0059] Of course the dielectric multilayer film forming the polarizedlight converter element and color separation/combining prism is appliedto allow only a designated light wavelength from the input lightthrough, in order to obtain a peak value of the permeance rate orreflection rate of that P polarized light or the permeance rate orreflection rate of that S polarized light, or permeance rate orreflection rate for a circular polarized light. The dielectricmultilayer film allows only a limited light wavelength through, forexample, a G exclusive beam splitter is coated with a dielectricmultilayer film ideal for G light exclusively for a wavelength band inthe vicinity from 500 nm to 600 nm, and utilizing an R-B exclusivepolarized beam splitter 16 RB coated with a dielectric multilayer filmideal for R light and B light exclusively for the two wavelength bandsin the vicinity from 400 nm to 500 nm and from the vicinity of 600 nm to700 nm means that a dielectric multilayer film can easily be formed, andalso that the permeance rate and reflective rate and further the (light)analyzing efficiency are improved compared to the related art. Areflective liquid crystal display device for high accuracy colorrestoration and high luminance, and high efficiency contrast cantherefore be provided. By also adding an inclined (sloping) film or inother words a dielectric multilayer film whose film thickness changesaccording to the input angle of the light, an image of higher uniformityand high color purity can be obtained.

[0060] The light emitted from the exclusive polarized beam splitter 16RB is converted to one-way R light or B light by the designatedwavelength converter element 18, and both the R light and B lightconverted to S polarized light are input to the dichroic mirror 19.

[0061] The RGB light constituting the image is afterwards recombined bya color combining mirror such as the dichroic mirror 19 or a dichroicprism not shown in the drawing, and the light passed through aprojection means 20 (for example a projection lens) such as a zoom lensand then arrives on the screen. The image formed by the reflectiveliquid crystal display elements 2R, 2G, 2B is shown as an enlargedprojection image on the screen by the projection means 20. Thereflective liquid crystal display device utilizing these threereflective liquid crystal display elements drives the lamp and the panelby means of a power supply 21.

[0062] The reflective liquid crystal display of the related artseparates the light from the light source into the three colors R G Bwith at least one or more color separator prisms or color separatormirrors, analyzes each of the R G B light with at least three or morepolarized beam splitters and after combining the three colors with thecolor combining prisms further projects the image on the screen usingthe projection lens so that the device was large overall, had a heavyweight and tended to have a high cost. This invention along withachieving a compact and light-weight device by means of a structureutilizing two units constituted by a G exclusive and a R-B exclusivepolarized beam splitter, allows freely controlling the color purity,improves color irregularities and simultaneously improves performance. Aprojection type image display device, compact and with high brightnessand high image quality can therefore be provided. Further, a costreduction can be achieved because the number of component parts isreduced.

[0063]FIG. 2 is an overall plan view showing the second embodiment ofthe projection type liquid crystal image display device of theinvention.

[0064] The R G B color light emitted from reflective liquid crystaldisplay elements such as the reflective liquid crystal display elements2R, 2G, 2B, or reflective intense inductive image display elements ordrive micromirror image display elements, is analyzed by the polarizedbeams splitter 16G and polarized beam splitter 16RB that constitute thecolor separating/combination elements, and the color is then recombinedby the dichroic prisms 19 a and the light passes through a projectionmeans 20 such as a zoom lens and arrives on the screen. The image formedon the reflective liquid crystal display elements 2R, 2G, 2B by theprojection means 20 is projected as an enlarged image on the screen. Theprism 19 a of this invention has a size larger than the polarized beamsplitter so that the light beam is not eclipsed, and the overallstructure is compact so that the size is different to the beam splitter.The sloping (or inclining) film with the dichroic coating can be freelyset so that an image with a high uniform color purity can be provided.Also in the structure of the invention, a support section is installedfor an angle bevel 29 in the cabinet holding optical elements such as adichroic prism 19 a, by supporting the angle bevel 29 for the opticalelements, the positioning and maintaining of the optical element such asthe dichroic prism 19 a is easily accomplished, assembly time isshortened during production, and the overall cost of the projection typedisplay device can be reduced. The space savings achieved by this anglebevel 29 allow installing optical members for example a lens or otheroptical elements, to avoid the trouble from high density placement ofcomponents and achieve a compact device.

[0065]FIG. 3 is an overall plan view showing the third embodiment of theprojection type liquid crystal image display device of the invention.

[0066] The light passes the condenser lens 30 and in order to illuminatethe reflective liquid crystal display elements 2R, 2G, 2B for each R G Bcolor, the light of a designated wavelength band is first converted to apolarization direction by means of a designated wavelength converterelement 28. In this case, if the illuminating light is S polarized lightthen it is converted to P polarized light, and separated into each colorby the wideband polarized beam splitter 16 RGB. If for instance Gpolarized light is converted by the designated wavelength converterelement 28, the light is divided into two portions, one G light and theother R, B light by the polarized beam splitter 16 RGB and then input tothe respective exclusive polarized color separator/synthesizer elementconsisting of polarized beam splitters 16G, 16RB. In other words, the Ppolarized light of the G light is converted into S polarized light bythe designated wavelength converter element 27, input to the G exclusivepolarized beam splitter 16G, and then reflected back to the G exclusivereflective liquid crystal display element 2G since the light is Spolarized light, and beamed onto the liquid display element 2G. Also,the B light and R light passes the B-R exclusive polarizing plate 14, isbeamed onto the R-B exclusive beam splitter 16 RB, and then transits theR-B exclusive beam splitter 16 RB to convert only light on thedesignated wavelength band to the polarization direction, and thepolarized light of either the B light or the R light is converted from Spolarized light to P polarized light and the B light for exampleconverted to P polarized light, transits the R-B exclusive beam splitter16 RB and illuminates the B exclusive reflective liquid crystal displayelement 2B. The R light on the other hand is an S polarized light soafter being reflected by the R-B exclusive beam splitter 16 RB isilluminated onto the R exclusive reflective liquid crystal displayelement 2R.

[0067] The above description is of course only one specific example andthis invention is not limited to this example. A structure may also beutilized wherein the R light may be converted into P polarized light,the polarized light of a different lighting system may originally be Ppolarized light, and one color from R G B is converted to S polarizedlight and the remaining two colors be P polarized light. An RB exclusiveinput light polarizing plate 14 and a G exclusive input light polarizingplate 15 maybe installed on the incident side for the S polarized lightto permeate each of the exclusive color reflective liquid crystalelements 2R, 2G, 2B, and the degree of deflection of each color andcolor purity enhanced. Afterwards, the polarized light is converted bythe reflective image display element 2 for each exclusive color, thelight input again to the polarized beam splitters 16G, 15RB for eachexclusive color, the S polarized light reflected and the P polarizedlight permeates through.

[0068] A plurality of reflective liquid crystal display elements 2 areformed to correspond to the number of display pixels (for example, 1024horizontal pixels and 768 vertical pixels for each of the three colors,etc.). The light polarization angle of the pixels matching the liquidcrystal display elements 2 changes according to an external drivesignal, and ultimately a light is output in the polarization directionof the input beam and an intersecting direction, and light matching thepolarized light direction is analyzed by the polarized beam splitter 16.The light intensity passing through the polarized beam splitter and theanalyzed light intensity are determined for light along the deflectionlight angle, by its relation with the polarization angle of thepolarized beam splitter 16. The image is in this way projected accordingto an externally input signal. At this time, the polarization directionis the same as the input light in the polarized light converter elementsconstituted by the B exclusive beam splitter 16G and the R-B exclusivebeam splitter 16RB of this invention, when a black display is shown onthe reflective liquid crystal display elements 2R, 2G, 2B, and the lightreturns as is, along the light input path, to the light source side.

[0069] The RGB light constituting the image is afterwards recombined bya color combining mirror such as the dichroic mirror 19 or a dichroicprism not shown in the drawing, and the light passed through aprojection means 20 (for example a projection lens) such as a zoom lensand then arrives on the screen. The image formed by the reflectiveliquid crystal display elements 2R, 2G, 2B is shown as an enlargedprojection image on the screen by the projection means 20. Thereflective liquid crystal display device utilizing these threereflective liquid crystal display elements drives the lamp and the panelby means of a power supply 21.

[0070] The reflective liquid crystal display of the related artseparates the light from the light source into the three colors R G Bwith at least one or more color separator prisms or color separatormirrors, analyzes each of the R G B light with at least three or morepolarized beam splitters and after combining the three colors with thecolor combining prisms further projects the image on the screen usingthe projection lens so that the device was large overall, had a heavyweight and tended to have a high cost. This invention along withachieving a compact and light-weight device by means of a structureutilizing two units constituted by a G exclusive and a R-B exclusivepolarized beam splitter, allows freely controlling the color purity,improves color irregularities and simultaneously improves performance.The color separation mean combines the polarized beam splitter withdesignated wavelength converter elements so that there are few of theeffects accompanying angular dependence and consequently calculating thecolor performance is easy. A projection type image display device, thatis compact and has high brightness and high image quality can thereforebe achieved. Further, a cost reduction can be achieved because thenumber of component parts is reduced.

[0071]FIG. 4 is an overall plan view showing the fourth embodiment ofthe projection type liquid crystal image display device of theinvention.

[0072] In addition to the effect of the embodiment of FIG. 3, the R G Bcolor light emitted from the reflective liquid crystal display elements2R, 2G, 2B is analyzed by the polarized beams splitter 16G and polarizedbeam splitter 16RB that constitute the color separating/combinationelements, and the light for R G B color is then recombined by thedichroic prisms 19 a and the light passes through a projection means 20and arrives on the screen. The image formed on the reflective liquidcrystal display elements 2R, 2G, 2B by the projection means 20 isprojected as an enlarged image on the screen. The prism 19 a of thisinvention has a size larger than the polarized beam splitter so that thelight beam is not eclipsed, and the overall structure is compact so thatthe size is different to the polarized beam splitter. The sloping (orinclining) film of the dichroic coating can be freely set so that animage with a high uniform color purity can be provided.

[0073] Also in the structure of the invention, a support section isinstalled with a support section for angle bevel 29 in a cabinet holdingoptical elements such as a dichroic prism 19 a. By supporting the anglebevel 29 for the optical elements, the positioning and maintaining of anoptical element such as the dichroic prism 19 a are easily accomplished,assembly time is shortened during production, and the overall cost ofthe projection type display device can also be reduced. The spacesavings achieved by this angle bevel 29 allow installing optical membersfor example polarized light separating elements constituted by apolarized beam splitter 16 RGB, to avoid the trouble resulting from highdensity placement of components and achieve a compact device. FIG. 5 isan overall plan view showing the fifth embodiment of the projection typeliquid crystal image display device of the invention, and shows inparticular the structure of the optical system.

[0074] In FIG. 5, a light source unit comprised of a reflector 2 and alight source 1 is installed in the image display device. The lightemitted from the light source unit passes through a polarity rectifierelement 31 such as a polarizing plate or polarizing beam splitter (PBS),and light rectified as P polarized light is separated into G light(green light) and, R light (red light) and B light (blue light) by thegreen color separator mirror 13. The separated G light is input to thepolarized beam splitter 16B, the input light permeates through as Ppolarized light, is input to the image display element constituted byreflective liquid crystal display element 2G, the polarized convertedlight is received and reflected according to the video signal, and inputagain to the polarized beam splitter 16G. The polarized beam splitter16G analyzes the input light according to the polarization conversionlevel received per the reflective liquid crystal display element 2G, orin other words reflects only the S polarization components of thepolarized converted light from among the light that was input, andobtains the image.

[0075] The R light and the B light separated by the green colorseparation mirror 13 are input to the polarized beam splitter 16RB onlyas R light S polarized light. The R light which is S polarized light isreflected by the polarized beam splitter 16RB and input to thereflective liquid crystal display element 2R.

[0076] The light input to the reflective liquid crystal display element2R is received and reflected as polarized light, according to the imagesignal and input again to the polarized beam splitter 16RB. In thepolarized beam splitter 16RB, the light is analyzed according to thepolarized light conversion level received by the reflective liquidcrystal display element 2R, and an image obtained. The B light permeatesthe polarized beam splitter 16RB as P polarized light, and is input tothe reflective liquid crystal display element 2B. The light input to thereflective liquid crystal display element 2B receives polarityconversion according to the video signal, is reflected and is inputagain to the polarized beam splitter 16RB. In the polarized beamsplitter 16RB, the light is analyzed according to the polarized lightconversion level received by the reflective liquid crystal displayelement 2B, and an image obtained.

[0077] Though not shown in the drawing, the S polarized light of justthe B light may be polarized-converted by the designated wavelengthconverter element 17 the converts a designated light wavelength into apolarized direction. The S polarized light of the polarity converted Blight is at this time input to the polarized beam splitter 16RB. The Blight consisting of S polarized light is reflected by the polarized beamsplitter 16RB, and input to the reflective liquid crystal displayelement 2B. The light input to the reflective liquid crystal displayelement 2B receives polarity conversion according to the video signal isreflected and is input again to the polarized beam splitter 16RB. In thepolarized beam splitter 16RB, the light is analyzed according to thepolarized light conversion level received by the reflective liquidcrystal display element 2B, and an image obtained. The R light permeatesthe polarized beam splitter as P polarized light, and is input to theeffective liquid crystal display element 2R. The light input to thereflective liquid crystal display element 2R receives polarityconversion according to the video signal is reflected and is input againto the polarized beam splitter 16RB.

[0078] In the polarized beam splitter 16RB, the light is analyzedaccording to the polarized light conversion level received by thereflective liquid crystal display element 2R, and an image obtained.

[0079] The respective images of the red, blue and green light that wereobtained are combined (synthesized) by a color combining means 19 suchas for example a dichroic mirror or a dichroic prism, and projected bymeans of the projection lens 20. A designated wavelength converterelement 18 to convert the polarity direction of a designated wavelengthmay be inserted on the output side of the polarized beam splitter 16RBat this time, to align the polarity directions of the R light and Blight. A polarization screen can also be used at this time settingdesignated wavelength converter elements 18 to convert the polaritydirection of designated wavelengths for all the R light, G light and Blight, for aligning their polarity directions.

[0080] Alternatively, a polarization converter element 32 can beinstalled on the optical path of the G light to convert light analyzedby the polarized beam splitter 16G from S polarized light to P polarizedlight, and input the P polarized light to the color combining means suchas a color combining mirror 19. Further, designated wavelength bands canbe set with a designated wavelength converter element 18 topolarity-convert light on a designated wavelength so that either or boththe R light or B light polarity directions are S polarized light. Thepermeance band of the G light is in this way widened and either or bothof the R light, B light reflection bands are capable of being widened bymeans of the polarity characteristics of the dichroic mirror or thedichroic coating constituting the color combining means 19.

[0081] The polarity rectifier elements 33, 34, 35 such as polarizingplates may be installed on the incident side or the output side of thepolarized beam splitter 16G or the polarized beam splitter 16RB. At thistime, the polarity rectifier element 33 installed on the incident sideof the polarized beam splitter 16RB on the R or B optical path, isinstalled on the incident side of the optical element 17 for convertingthe polarization direction of the designated wavelength band. Also, thepolarity rectifier element 35 installed on the incident side of thepolarized beam splitter 16RB, is installed onto he output side of thedesignated wavelength converter element 18 for converting thepolarization direction of the designated wavelength band.

[0082] The structure of this invention utilizing two polarized beamsplitters, along with being compact and lightweight, can freely regulatethe color purity and improves color irregularities.

[0083]FIG. 6 is an overall plan view showing the sixth embodiment of theprojection type liquid crystal image display device of the invention,and indicates the structure of the optical system.

[0084] In FIG. 6, a light source unit comprised of a reflector 2 and alight source 1 is installed in the image display device, the lightsource 1 is a white color lamp. The light emitted from the light sourceunit passes through a polarity rectifier element 8 such as a polarizingplate or a polarization conversion element (polarizing beam splitter),and the light rectified as S polarized light is separated into G light(green light) and, R light (red light) and B light (blue light) by thegreen color separator mirror 13.

[0085] The separated G light is input to the polarized beam splitter16G, the input light permeating through as S polarized light, is inputto the image display element constituted by reflective liquid crystaldisplay element 2G, the polarized converted light is received andreflected according to the video signal, and input again to thepolarized beam splitter 16G.

[0086] The polarized beam splitter 16G analyzes the input lightaccording to the polarization conversion level received per thereflective liquid crystal display element 2G, or in other words reflectsonly the P polarization components of the polarized converted light fromamong the light that was input, and obtains the image.

[0087] The R light and the B light separated by the green colorseparation mirror 13 are input to the polarized beam splitter 16RB onlyas R light S polarized light by the optical element 17 for convertingthe polarization direction of the designated wavelength band. The Rlight which is P polarized light permeates per the polarized beamsplitter 16RB and is input to the reflective liquid crystal displayelement 2R.

[0088] The light input to the reflective liquid crystal display element2R is received and reflected as polarized light, according to the imagesignal and input again to the polarized beam splitter 16RB. In thepolarized beam splitter 16RB, the light is analyzed according to thepolarized light conversion level received by the reflective liquidcrystal display element 2R, and an image obtained. The B light permeatesthe polarized beam splitter 16RB as S polarized light, and is input tothe reflective liquid crystal display element 2B. The light input to thereflective liquid crystal display element 2B receives polarityconversion according to the video signal, is reflected and is inputagain to the polarized beam splitter 16RB. In the polarized beamsplitter 16RB, the light is analyzed according to the polarized lightconversion level received by the reflective liquid crystal displayelement 2B, and an image obtained.

[0089] Though not shown in the drawing, the P polarized light of justthe B light may be polarized-converted by the designated wavelengthconverter element 17 that converts a designated light wavelength into apolarized direction. The P polarized light of the polarity converted Blight is at this time input to the polarized beam splitter 16RB. The Blight consisting of P polarized light permeates through the polarizedbeam splitter 16RB, and is input to the reflective liquid crystaldisplay element 2B. The light input to the reflective liquid crystaldisplay element 2B receives polarity conversion according to the videosignal is reflected and is input again to the polarized beam splitter16RB. In the polarized beam splitter 16RB, the light is analyzedaccording to the polarized light conversion level received by thereflective liquid crystal display element 2B, and an image obtained. TheR light permeates the polarized beam splitter as S polarized light, andis input to the reflective liquid crystal display element 2R. The lightinput to the reflective liquid crystal display element 2R receivespolarity conversion according to the video signal is reflected and isinput again to the polarized beam splitter 16RB.

[0090] In the polarized beam splitter 16RB, the light is analyzedaccording to the polarized light conversion level received by thereflective liquid crystal display element 2R, and an image obtained.

[0091] The respective images of the red, blue and green light that wereobtained are combined (synthesized) by a color combining means 19 suchas for example a dichroic mirror or a dichroic prism, and projected bymeans of the projection lens 20. A designated wavelength converterelement 18 to convert the polarity direction of a designated wavelengthmay be inserted on the output side of the polarized beam splitter 16RBat this time, to align the polarity directions of the R light and Blight. A polarization screen can also be used at this time settingdesignated wavelength converter elements 18 to convert the polaritydirection of designated wavelengths for all the R light, G light and Blight, for aligning their polarity directions.

[0092] Alternatively, at this time, designated wavelength bands can beset with a designated wavelength converter element 18 topolarity-convert light on a designated wavelength so that either or boththe R light or B light polarity directions on the R light and B lightoptical paths are S polarized light. The permeance band of the G lightis in this way widened and either or both of the R light, B lightreflection bands are capable of being widened by means of thepolarization characteristics of the dichroic mirror or the dichroiccoating constituting the color combining means 19.

[0093] The polarity rectifier elements 33, 34, 35 such as polarizingplates may be installed on the incident side or the output side of thepolarized beam splitter 16G or the polarized beam splitter 16RB. At thistime, the polarity rectifier element 33 installed on the incident sideof the polarized beam splitter 16RB on the R or B optical path, isinstalled on the incident side of the optical element 17 for convertingthe polarization direction of the designated wavelength band. Also, thepolarity rectifier element 35 installed on the incident side of thepolarized beam splitter 16RB on the optical path of the R light and Blight, is installed on the light output side of the designatedwavelength converter element 18 for converting the polarizationdirection of the designated wavelength band.

[0094] The structure of this invention utilizing two polarized beamsplitters, along with being compact and lightweight, can freely regulatethe color purity and improves color irregularities.

[0095]FIG. 7 is an overall plan view showing the seventh embodiment ofthe projection type liquid crystal image display device of theinvention.

[0096] The embodiment of FIG. 7 shows a three plate type projectiondisplay device using a total of three plates corresponding to the threeprimary colors, R (red), G (green) and B (blue) constituted by thereflective liquid crystal display elements 2R, 2G, 2B as the liquidcrystal light valves.

[0097] The light source 1 in the projection type liquid crystal displaydevice of FIG. 7 is a white color lamp.

[0098] The light emitted from the light source 1 is reflected from atleast one reflective surface mirror 5 having an output aperture of acircular or a polygonal shape. The light passes through the reflectiveliquid crystal display elements 2R, 2G, 2B constituting the liquidcrystal light valves, progresses towards the projection lens 20 and isprojected on the screen.

[0099] A dichroic prism or a dichroic mirror 13 as the color separatingmeans between the polarized beam splitter 8 and the reflective liquidcrystal display elements 2, permeates or reflects only the G light fromamong the three light colors of R light, B light, G light, and the Glight is separated from the other B light and G light. The G lightseparated by the dichroic mirror 13 is permeated or reflected by thepolarized beam splitter 16G. The polarizing plates 15, 29 having apolarizing rectifying effect on the G light may be installed on theincident side or the output side of the polarized beam splitter 16G atthis time. The light input onto the liquid crystal display element 2G isrespectively modulated and readout light, reflected and sent outward,and the modulated light is respectively analyzed by the polarized beamsplitter 16 G. The R light and B light separated from the G light,permeate through a designated wavelength converter element 17 forpolarization conversion only at a band above or below a specifiedwavelength from approximately 510 nm to 580 nm, and either or any of theB light or the R light polarized light color is changed, and thepolarization directions of the R light and B light intersect each other.The light is then input to the polarized beam splitter 16RB, andseparated into R light and B light having different polarizationdirections, and input into the respective reflective liquid crystaldisplay elements 2R, and 2B. The polarizing plates 14 having apolarizing rectifying effect may be installed on the incident side ofthe designated wavelength converter element 17. Further, the designatedwavelength converter element 18 for polarization-conversion only of thebands above or below the designated wavelength from approximately 510 nmto 580 nm, may be installed on the output side of the polarized beamsplitter 28RB. Also, prior to this installation, a polarizing plate 29having a rectifying effect, may be installed on the output side of thedesignated wavelength converter element 18.

[0100] The light input to the reflective liquid crystal display elements2R, and 2B is respectively modulated, reflected and sent outward asreadout light corresponding to each color per the liquid crystal displayelement, and the modulated light of each color is respectively analyzedby the polarized beam splitter RB. The analyzed R light and G light andB light are combined by the dichroic prism or the dichroic mirror 19constituting the color combining filter, the light permeates through theprojection means 20 and arrives on the screen 20. By setting thedesignated wavelength converter element 18 so that the light the opticalpath permeating the color combination filter is P polarized light, andso that the light on the optical path reflecting from the colorcombination filter is S polarized light, the permeance and reflectancebands of the color combination filter broaden and a high efficiencyoptical system can be achieved. The image formed on the liquid crystalelement 2 by the projection means 20 is projected on the screen as anenlarged image as a function of a display device. The polarizing platesare installed on the input and the output of the polarized beam splitterso that the contrast is improved.

[0101] This invention along with achieving a compact and light-weightdevice by means of a structure utilizing two polarized beam splitterunits, allows freely controlling the color purity, improves colorirregularities and simultaneously improves performance. A projectiontype image display device, compact, with high brightness and high imagequality can therefore be provided. Further, a cost reduction can beachieved because the number of component parts is reduced.

[0102] The eighth embodiment of the optical unit of the invention isnext described while referring to FIG. 8.

[0103]FIG. 8 is an overall plan view showing the eighth embodiment ofthe optical unit used in the image display device of the invention. Thelight is shown by solid lines and dotted lines. The solid lines are theS polarized light and the dotted lines are the P polarized light. In thefigure, the light from the light source (not shown in the drawing)passes along the polarization converter element 101 typified by astructure combining a ½ wavelength plate and a polarization beamsplitter prism, and the P polarized light is converted into S polarizedlight, and the S polarized light is emitted unchanged as S polarizedlight.

[0104] The polarization converter element 101 may be utilized forconverting S polarized light to P polarized light. The example for thisembodiment describes the case of converting P polarized light to Spolarized light by utilizing the polarization converter element 101.

[0105] Of the S polarized light permeating the polarization converterelement 101, the B light permeates through a dichroic mirror such as thecolor separation mirror 102, permeates the polarizing plate 103 a and apolarization converter element 115 (polarization designated wavelengthconverter element may also be used) for a ½ wavelength plate, and acolor alignment film 104 a, and is input to the polarization beamsplitter 105 RGB. The polarizing plate 103 a is used for removing the Ppolarized light mixed in with the S polarized light which is theessential light. The color alignment film 104 a is described in detaillater on. After the B light consisting of S polarized light is convertedfrom S polarized light to P polarized light in the polarizationconverter element 115, the B light permeates the polarization beamsplitter 105 RGB and is input to the full reflecting prism 108 and ishere reflected. The B light in input to the reflecting liquid crystalelement 107B by way of the ¼ wavelength plate, and the P polarized lightis converted to S polarized light in the reflecting liquid crystalelement 107B, and after again being reflected by the full reflectingprism 108 is input to the color combining polarized beam splitter (ordichroic prism) 105 RGB, and here is reflected and output to theprojection lens (not shown in the drawing). The ¼ wavelength plate 106 ais used mainly for the purpose of aligning the deflecting optical pathof the liquid crystal display element 107B, the polarized beam splitter105RGB, and the lighting system of the polarized optical path.

[0106] The R light and the G light constituted by S polarized lightreflected by the color separation mirror 102 is reflected by thereflection mirror 109 and after passing through the polarizing plate 103b to remove the S polarized light is input to the designated wavelengthconverter element 112 a. Here, the S polarized R light is converted to Ppolarized light, and the G light remains as S polarized light andpermeates the color alignment film 104 b, is input to the colorseparation/combination polarized beam splitter 105RG.

[0107] The S polarized G light is reflected by the polarized beamsplitter 105RG, permeates the ¼ wavelength plate 106 b and is input tothe G light reflective liquid crystal element 107G. The S polarizedlight is converted to P polarized light in this reflective liquidcrystal element 107G, reflected and once again input as P polarizedlight to the polarized beam splitter 105RG, permeates through thepolarized beam splitter 105RG and enters the designated wavelengthconverter element 112 b.

[0108] The R light converted to P polarized light permeates through thecolor separation/combination polarized beam splitter 105RG and afterpermeating through the ¼ wavelength plate 106 c, is input to the R lightreflective liquid crystal display element 107R. In this reflectiveliquid crystal display element 107R, the P polarized light is convertedto S polarized light, reflected and output as S polarized light. The Spolarized R light is reflected by the polarized beam splitter 105RG andinput to the designated wavelength converter element 112 b. in thedesignated wavelength converter element 112 b, the S polarized R lightis converted to P polarized light and the P polarized G light permeatesthrough unchanged. The P polarized components contained in the Ppolarized G light and R light are removed by the polarizing plate 103 cto prevent deterioration of the contrast, and then are input to thecolor combining polarized beam splitter (or dichroic prism) 105RGB. TheP polarized G light and R light permeates through the color combiningpolarized beam splitter (or dichroic prism) 105RGB, and the S polarizedB light is reflected by the polarized beam splitter (or dichroic prism)105RGB and input to the projection lens (not shown in drawing). The Ppolarized components mixed in with the B light permeate through herewithout being reflected by the polarized beam splitter 105RGB so thatthe P polarized components are not input to the projection lens.

[0109] In the embodiment of FIG. 8, the light input to the colorseparator mirror 102 is converted to S polarized light but a structureutilizing light converted to P polarized light may also be used.

[0110] The S polarized R light is converted into P polarized light bythe designated wavelength converter element 112 a but a structureconverting the G light into P polarized light may also be used.

[0111] The color alignment film 104 may for example be a dielectricmultilayer film vapor deposited on the direct polarized beam splitter ordichroic prism, and may be a color film or a color filter such as ofcolored glass wherein a polarized beam splitter or a dichroic mirror isvapor deposited with a dielectric multilayer film on a glass plate or ½wavelength plate. What is essential is that any suitable material becapable of lowering the permeance rate of the designated wavelengthregion.

[0112] In this embodiment, the full reflecting mirror is not alwaysrequired and the may be installed facing the output surface of the Blight of the color combining polarized beam splitter 105 RGB.

[0113] However, since the height of the optical path R, G, B light canbe aligned by installing the full reflecting prism such as in thisembodiment, the efficiency of each light color is good, and asatisfactory contract can be obtained.

[0114] The ninth embodiment of the optical unit of the invention is nextdescribed while referring to FIG. 9.

[0115]FIG. 9 is an overall plan view showing the ninth embodiment of theoptical unit used in the image display device of the invention. Thelight is shown by solid lines and dotted lines. The solid lines are theS polarized light and the dotted lines are the P polarized light. In thefigure, the light from the light source (not shown in the drawing)passes along the polarization converter element 101 (not shown in thedrawing) typified by a structure combining a ½ wavelength plate and apolarization beam splitter prism, and the P polarized light is convertedinto S polarized light, and the S polarized light is emitted unchangedas S polarized light.

[0116] In FIG. 9, the B light permeates the color separating mirror 102and the P polarized light contained in the S polarized light componentsare removed in the polarizing plate 103 a and after the light isconverted to P polarized light in the polarization converter element115, the light permeates the polarization beam splitter 105 RGB and isreflected by the full reflecting prism 108. The light is then input tothe reflecting liquid crystal element 107B by way of the ¼ wavelengthplate 106 a. The G light input to the reflecting liquid crystal element107B is here converted into S polarized light and after once againpermeating the ¼ wavelength plate 106 is reflected by the fullreflecting prism 108 and input to the polarized beam splitter 105RGB.The G light is S polarized light and so this time is reflected by thepolarized beam splitter 105RGB.

[0117] After the S polarized R light and B light permeate through thepolarizing plate 103 b, they are reflected by the reflecting prism 110,and permeate the designated wavelength converter element 112 a. The Spolarized R light and B light are converted to P polarized light in thedesignated wavelength converter element 112 a, and the R light permeatesthrough unchanged as S polarized light. The B and R light are input tothe color separating and color combining polarized beam splitter 105RB.The B light is P polarized light so it permeates through the polarizedbeam splitter 105RB, permeates through the ¼ wavelength plate 106 b andis input to the liquid crystal display element 107B. Here the light isconverted to S polarized light and reflected, is input again to thepolarized beam splitter 105RGB by way of the ¼ wavelength plate 106 band here, the light is reflected. The R light is S polarized light so isreflected by the polarized beam splitter 105RB and is input to theliquid crystal display element 107B by way of the ¼ wavelength plate 106c. Here, after being converted to P polarized light it once again passesthrough the ¼ wavelength plate 106 c and is input to the polarized beamsplitter 105RGB. The R light is P polarized light and so this timepermeates through the polarized beam splitter 105RGB. The R light and Blight emitted from the polarized beam splitter 105RGB are input to thedesignated wavelength converter element 112 b. The designated wavelengthconverter element 112 b converts the S polarized B light into Ppolarized light , and the P polarized R light is permeated through as iswithout changes. The R light and B light that permeated through thedesignated wavelength converter element 112 b is input to the colorcombining polarized beam splitter 105RGB. The R light and B light areboth P polarized light and so permeate through the polarized beamsplitter 105RGB and are input to the designated wavelength converterelement 112 c. The designated wavelength converter element 112 cconverts the G light from S polarized light to P polarized light.Accordingly, the R light, G light and B light permeate through thepolarizing plate 103 c as P polarized light and are input to theprojection lens (not shown in drawing) . The polarization directions ofthe R light and B light are not limited to the above directions, and theR light can input as is, as P polarized light, and the G light can beinput as is, as S polarized light into the polarized beam splitter105RB.

[0118]FIG. 10 is an overall plan view showing the tenth embodiment ofthe optical unit used in the image display device of the invention. Thelight is shown by solid lines and dotted lines. The solid lines are theS polarized light and the dotted lines are the P polarized light.

[0119] In this figure, the polarization direction of the R light, Glight and B light converted to S polarized light by the polarizationconverter element (not shown in drawing) are input to the designatedwavelength converter element 112 d. Here, the point that the B light isconverted to P polarized light, the point that a color separation beamsplitter 11 is installed instead of the color separation mirror 102, andthe point that a full reflecting prism 110 is installed instead of thereflecting mirror 109 are the points different from the embodiment ofFIG. 8.

[0120] After the B light is converted from S polarized light to Ppolarized light by the designated wavelength converter element 112 d,the B light permeates through the polarized beam splitter 111, andpermeates through the color alignment film 104, the polarizing plate 103(one example of rectification by a polarizing plate), and is input tothe color combining polarized beam splitter 105RGB. The B light fromthen onward is it output from the polarized beam splitter 105RGB afterpassing through the same path as in the embodiment of FIG. 8. After theS polarized R and G light are reflected by the full reflecting mirror110, the R and G light are input to the polarizing plate 103. The R andB light are afterward subjected to the same processing as in FIG. 8, andemitted from the polarized beam splitter 105RGB. The polarizing plate103 may be installed at the position of the designated wavelengthconverter element 112 d, and the polarizing plate, vapor depositionpolarizing plate, polarizing separation sheet, etc., may be adhered tothe prism 111 along with the designated wavelength converter element 112d. In this case, the prism 11, 110, polarizing beam splitter 105RGB andfull reflecting mirror 108 can all be made to adhere, and the assemblyoperation thus improved. The alignment of the optical path is also easy.

[0121]FIG. 11 is an overall plan view showing the eleventh embodiment ofthe optical unit used in the image display device of the invention. Thelight is shown by solid lines and dotted lines. The solid lines are theS polarized light and the dotted lines are the P polarized light.

[0122] In this embodiment, the P polarized light from among the light ofthe optical unit permeates the polarization converter element (not shownin drawing) unchanged, and the S polarized light is converted to Ppolarized light. In the designated wavelength converter element 112 donly the G light is converted to S polarized light and is input to thepolarized beam splitter 111, and here only the S polarized G light isreflected, and further is reflected at the full reflecting prism 108,and is input to the G light liquid crystal display element 107G by wayof the ¼ wavelength plate 106 a, and input as P polarized light to thepolarized beam splitter 111. Since the G light is P polarized light, itpermeates this time through the polarized beam splitter 111, and furtherpermeates through the polarizing plate 103 a, color combining polarizedbeam splitter 105RGB and is input to the projection lens (not shown indrawing). The B light and R light are P polarized light and thereforepermeate through the color separating polarized beam splitter 111 andthe polarizing plate 103, and are input to the designated wavelengthconverter element 112 a. In the designated wavelength converter element112 a, the R light is converted into S polarized light, and the B lightis input unchanged as P polarized light to the colorseparating/combining (or analyzing) polarized beam splitter 105RB. Sincethe R light is S polarized light, it is reflected at the polarized beamsplitter 105RB and is input to the R light liquid crystal displayelement 107R by way of the ¼ wavelength plate 106 b, the light convertedto P polarized light and permeated through the polarized beam splitter105RB. Since the B light is P polarized light, it permeates through thepolarized beam splitter 105RB and is input to the B light liquid crystaldisplay element 107B by way of the ¼ wavelength plate 106 c. Here, thelight is converted to S polarized light, and since the light this timeis S polarized light, it is reflected by the polarized beam splitter105RB and input to the designated wavelength converter element 112 b.

[0123] The R light is here converted to S polarized light, the B lightpermeates unchanged as converted S polarized light through thepolarizing plate 103 c and is reflected by the full reflecting prism117, and is input to the combining polarized beam splitter 105RB. Sincethe R light and B light are S polarized light they are reflected at thepolarized beam splitter 105RB, and input to the projection lens (notshown in drawing). In this embodiment, the polarizing plate 103 a is notnecessary, and in that case the full reflecting prism 108, polarizedbeam splitters 111, 105RG, the full reflecting prism 117 can all beadhered.

[0124]FIG. 12 is an overall plan view showing the twelfth embodiment ofthe optical unit used in the image display device of the invention. Thelight is shown by solid lines and dotted lines. The solid lines are theS polarized light and the dotted lines are the P polarized light.

[0125] This embodiment differs from the embodiment of FIG. 10 in thepoint that a polarizing converter element 115 is installed instead ofthe designated wavelength converter element 112 d, in the point that adichroic prism is installed instead of a polarized beam splitter 111,and in the point that the position of the liquid crystal display element107 is different. The color alignment film 104 is not shown in thedrawing but the position is the same as in FIG. 8 and FIG. 10 so adescription is omitted here.

[0126] In this embodiment, the R light, G light and B light areexplained as being S polarized light. The G light permeates the dichroicprism 111 b, and polarizing plate 103 and is converted to P polarizedlight by the polarized converter element 115, permeates through thepolarized beam splitter 105RGB, is reflected by the full reflectingprism 103, and is input to the G light liquid crystal display element107G by way of the ¼ wavelength plate 106 a. The light is afterwardsagain input to the polarized beam splitter 105RGB by the same path asthe B light of FIG. 10, and is here reflected.

[0127] The R light and B light on the other hand, is reflected by thedichroic prism 111 b and reflected by the full reflective prism 110, thelight permeates the polarizing plate 103 b, and the S polarized B lightis converted to P polarized light by the designated wavelength converterelement 112 a, and the R light is input to the colorseparation/combining polarized beam splitter 105RB without thepolarization direction being changed. The P polarized B light permeatesthrough the polarized beam splitter 105RB, permeates through the ¼wavelength plate 106 c and is reflected as S polarized light in theliquid crystal display element 107B. The B light is further reflected bythe polarized beam splitter 105RB, converted to P polarized light by thedesignated wavelength converter element 112 b, and after permeating thepolarizing plate 103 c, permeates the polarized beam splitter 105RB.Since the R light is S polarized light, it is reflected by the colorseparation/combining the polarized beam splitter 105RB, permeates the ¼wavelength plate 106 b, is reflected as P polarized light by the liquidcrystal display element 107R, permeates the polarized beam splitter105RB constituting the analyzing light, permeates the polarized beamsplitter 105RB unchanged, and after the polarity is rectified by thepolarizing plate 103 c, permeates the polarized beam splitter 105RB. Ofthe R light, B light and G light, the G light is changed to P polarizedlight in the designated wavelength converter element 112 c. Therefore,the R light, B light and G light are together polarity rectified as Ppolarized light by the polarizing plate 103 d and afterwards input tothe projection lens (not shown in drawing). Accordingly, the polarizingplate 103 c may be eliminated, and polarity rectification performed onall the R light, G light and B light by the polarizing plate 103 d.Further, the polarizing plate 103 c need not be cooled, the structure isalso simple, and the back focus distance is short and so is opticallyadvantageous.

[0128]FIG. 13 is an overall plan view showing the thirteenth embodimentof the optical unit used in the image display device of the invention.The light is shown by solid lines and dotted lines. The solid lines arethe S polarized light and the dotted lines are the P polarized light.

[0129] The embodiment of FIG. 13 differs from the embodiment of FIG. 11in the point that a designated wavelength converter element 112 c isinstalled on the output side of the polarized beam splitter 105RB, andfurther in that a polarizing plate 103 c between the fully reflectingprism 117 and the polarized beam splitter 105RB in FIG. 11 is hereinstalled on the output side of the designated wavelength converterelement 112 c, and that the polarizing plate 103 c has been removed frombetween the polarized beam splitter 105RB and the polarized beamsplitter 111.

[0130] After the G light has been reflected by the liquid crystaldisplay element 107G along the same path as in FIG. 11, the G lightpermeates the polarized beam splitter 105RB and the polarized beamsplitter 111 as polarized P light. After the R light and B light havebeen reflected by the respective liquid crystal display elements 107R,107B along the same path as in FIG. 11, the P polarized R light isconverted to S polarized light in the designated wavelength converterelement 112 b, and the R light and the B light are reflected as Spolarized light from the full reflecting prism 117, and furtherreflected by the polarized beam splitter 105RB. Afterwards, only the Glight is converted from P to S polarized light by the designatedwavelength converter element 112 c, the R light, G light and B light areall input as S polarized light to the projector lens (not shown indrawing) by way of the polarizing plate 103 c. Further, the colorseparation/combining function works adequately even if the designatedwavelength converter element 112 b and the polarizing plate 103 b areremoved. Also, if the sizes of the polarized beam splitters are set sothat the polarized beam splitter 105 is largest, polarized beam splitter105RB is smallest, and the polarized beam splitter 111 is midway betweenthese sizes, then even if the light input to the colorseparation/combining system from the lighting system is settelecentrically, the eclipsing of the input light by the polarized beamsplitter and the full reflecting prism can be prevented.

[0131]FIG. 14 is an overall plan view showing the fourteenth embodimentof the optical unit used in the image display device of the invention.The light is shown by solid lines and dotted lines. The solid lines arethe S polarized light and the dotted lines are the P polarized light.

[0132] The embodiment of FIG. 14 differs from the embodiment of FIG.8 inthe point that a condenser lens 119a has been installed between thecolor separation mirror 103 and the color combining polarized beamsplitter 105RGB, and in the point that a condenser lens 119 b has beeninstalled between the color separation mirror 102 and the reflectingmirror 109. Therefore, the reflection and the permeance paths of the Glight, R light and B light are the same.

[0133]FIG. 15 is an overall plan view showing the fifteenth embodimentof the optical unit used in the image display device of the invention.The light is shown by solid lines and dotted lines. The solid lines arethe S polarized light and the dotted lines are the P polarized light.

[0134] The embodiment of FIG. 15 differs from that of FIG. 9 in that acondenser lens 119 has been installed on the incident side of the colorseparation mirror 102, the reflection and the permeance paths of the Glight, R light and B light are the same as in FIG. 9.

[0135] The effect rendered by the embodiments from FIG. 8 through FIG.15 are next explained.

[0136] The liquid crystal display element 107B of FIG. 8, FIG. 10 andFIG. 14, and the liquid crystal display element 107G in FIG. 9, FIG. 11,FIG. 12, FIG. 13 and FIG. 15 need not always be reflected by the fullreflective prism 108, and need not face the direct combiningpolarization beam splitter 105RGB and polarization beam splitter 111.

[0137] The embodiments in FIG. 8 through FIG. 15 may be comprised of acolor separating means such as the color separator mirror 102, thepolarization beam splitter 111, and color separator dichroic prism 111b, and a color separating/combining means such as the colorseparation/combination polarization beam splitter 105RG, andpolarization beam splitter 105, and the color combining means shown bythe color combining polarization beam splitter. The RGB color separationand combining can therefore be achieved with a lightweight, low cost andsimple structure.

[0138] The optical path length of the R light, B light and G light canbe made to the same length by comprising all of the embodiments with afirst reflecting means such as a reflection mirror 109, and fullreflecting prism 110, 117, and a second reflecting means such as a fullreflecting prism 108. A structure configured in this manner along withbeing lightweight and low cost also allow various placements. In otherwords, instead of rectangular prism block, a triangular prism having thesame optical path length and made from the same glass material will bealmost twice as light and also reduce the cost for materials.

[0139] The reflecting means constituted by the reflecting mirror 109,full reflecting prisms 110, 117 and the full reflecting prism 108 canutilize aluminum, silver vapor deposition mirrors, reflective prisms ormirror vapor deposition prisms. The reflection rate can in this way beimproved and compactness and a lighter weight also achieved.

[0140] These reflecting means can also utilize a dichroic mirror ordichroic prism coated with a dielectric multilayer film. A reflectingmeans of this type allows cutting out unnecessary light and allowsaligning the color. Further, by utilizing the color alignment film inthis reflecting means, even finer color alignment can be achieved.

[0141] In the embodiments 8 through 10 of this invention, the R light, Glight and B light is separated by the color separating means constitutedby the color separation dichroic prism 111 b into a first, second andthird lights. The optical axis direction of the first and the secondlight is bent for example in an approximately right-angled direction bythe reflective mirror 109, and full reflective prisms 110, 117, etc, andinput to the color separation/combining means such as the polarized beamsplitter 105RG and polarized beam splitter 105RB. The light input tothis color separation/combining means is separated into a first and asecond light and mutually arrayed in a right angle, and input to imagedisplay elements constituted by light valves corresponding to therespective light colors, and the first light and the second lightreflected by these image display elements are input to a color combiningmeans. After the third light is separated by the color separating means,the light travels along the via the color combining means comprised by apolarized beam splitter 105RB installed in the direction of the opticalaxis at the output of the third light, and is bent for example in aright-angle direction by the second reflecting means, and input to theimage display element constituted by the light valve for the thirdlight, and after the image display devices constituted by light valvesreflect the respective colors of the light, the image light emitted fromthese image display devices is combined with the first and second lightper the color combining means. Accordingly, in this embodiment, thecontrast rate and the efficiency of each color of R light, G light and Blight as the first through third colors can be optimized.

[0142] Also in these embodiments, in the polarized light unified into Spolarized light or P polarized light by the lighting system, the twocolors of the first and second light from the R light, B light and Glight separated by the color separating means, the optical axis is bentat a right angle by the first reflecting means; and of the two colors ofthe first and second light, the first light is set in a polarizingdirection and the second light is set in a different direction by thedesignated wavelength converter element, so for example if the firstlight is S polarized light, then the second light color is input to thecolor separation/combining means after being converted to P polarizedlight. The light input to this color separating/combining means isseparated into a first light and a second light, mutually arranged intoright angles, and input to an image display element constituting thewrite valve for the corresponding light. After the remaining third lighthas been separated by the color separating means, a polarized converterelement such as the polarized converter element 115, ½ wavelength plateinstalled along the optical axis output of the third light is convertedto a polarization direction and for instance the S polarized light isconverted to P polarized light (See FIG. 8) and the light passes througha color combining means installed on the output side of this converterelement such as a polarized beam splitter 105RGB along the optical axisof the third light. The third light is further bent at a right angle bythe second reflecting means and input to the image display elementconstituted by a light valve matching the color of the third light. Inthis case, the light can simply be input to the image display elementconstituted by the light valve for that color by way of an optical mediamaterial such as glass or air, in the direction of the output axis ofthe of the color combining means, without using the second reflectingmeans. The light is reflected by the image display element constitutingthe light valve for the respective color. of the image light output fromthese image display elements, the first light is emitted from the imagedisplay element as P polarized light, the second color light is emittedfrom the image display element as S polarized light, and the secondlight color is emitted from the image display element as S polarizedlight and each, combined by the color combining/separating means such asthe polarized beam splitters 105RB, 105RG, or the black display lightanalyzed, and output in a direction intersecting the input optical axisof the color separation/combining means. Afterwards, the second colorlight is converted from S polarized light to P polarized light by thedesignated wavelength converter element installed on that optical axis(such as designated wavelength converter element 112 b), thepolarization direction aligned with the P polarized light of the firstlight color and input to the color combining means. On the other hand,after the image display element reflects the third light, thepolarization direction is changed by th image display element so that ifthe input light is P polarized it is changed to S polarized light, andinput to the color combining means by way of the second reflectingmeans. After the third light is reflected in the color combining means,it is combined with the P polarized first and second light, and outputto the third light color combining means from an output optical axisseparate from the input optical axis. Also, in the case of P polarizedlight input to the color separating means, the polarized converterelement 115 or ½ wavelength plate for the above described third lightare not required, and the P polarized light permeates as is, through thecolor separating means, and is input to the reflecting means. The firstlight and the second light must be respectively separated into Ppolarized and S polarized light so that as described above, a designatedwavelength converter element must be installed as a color separatingmeans on the light input/output optical path. In such a case, thepolarized converter element for the third light is eliminated so that areduced cost can be achieved.

[0143] In this embodiment, the first color separating means can reflectthe R light and the G light, and the B light made to permeate through asshown in the eighth embodiment. A structure can be utilized wherein theR light and the B light can be made to permeate by installing a colorcombining/separating prism on the input position of the light of thefull reflecting prism, and the B light reflected. Further, the R lightand B light can be made to permeate through and the G light reflected asshown by the embodiment of FIG. 11. Also in this structure, R light andG light can be made to permeate through and the B light may be returned.

[0144] Similarly, the R light and the B light can be reflected and the Glight made to permeate through as shown in FIG. 9. Alternatively, astructure may be employed wherein the R and B light can be made topermeate through and the G light returned by means of installing thecolor separating prism at the input position of the full reflectingprism 108.

[0145] A structure can also be used wherein the G light and B light arereturned, and the R light made to permeate through, or the G light and Blight made to permeate through and the R light returned.

[0146] Also, in this embodiment, the color separating means may becomprised of a dichroic prism or a dichroic mirror.

[0147] The color separator means and the color combining means may becomprised of a polarized separating/combining element constituted by apolarized beam splitter.

[0148] In this embodiment, a designated wavelength converter element isinstalled between the first color separating means and the colorseparating/combining means. Also, a structure comprised by designatedwavelength converter elements installed between a first color separatingmeans and a color combining means, and between a colorseparating/combining means and a color combining means may be used toimprove the efficiency of the R, G, B light and the contrast rate.

[0149] Further in these structures, a polarizing plate (or polarityrectifier element) may be installed between a first color separatingmeans and a color combining means, and between a colorseparating/combining means and a color combining means to improve theefficiency of the R, G, B light and the contrast rate.

[0150] Each color separating/combining means acquires a peak value ofoptical characteristic so that the permeance rate or the reflection(efficiency) rate for the two colors that are input are optimal. Forexample by a structure having a polarized beam splitter 105RG foroptimal characteristics in the color combining/separating means of the Rlight and B light, or a polarized beam splitter 105RB for optimalcharacteristics in the color combining/separating means of the R lightand B light, or a structure having a polarized beam splitter for optimalcharacteristics in the color combining/separating means of the G lightand B light. The efficiency of the R, G, B light and the contrast ratecan therefore be improved by using the above structures.

[0151] The color separating/combining means and the color combiningmeans consist of polarized light separation and elements for lightanalysis. Utilizing these elements allows the contrast rate of the R, G,B light to be improved.

[0152] The color separating/combining means and the color combiningmeans can eliminated the possibility of light eclipses by making thesize of the color separating/combining means larger than the size of thecolor combining means.

[0153] In this embodiment, a structure to combine the light of the onecolor (R light, G light, or B light) of S polarized light, with thelight of the two colors (R light, G light, or B light) consisting of Ppolarized light input from mutually intersecting directions by the colorcombining means, and the three colors emitted along the optical axis ofthe P polarized light.

[0154] In this embodiment, the optical axis of the projection means isparallel with the optical axis of the color combining means however theoptical axis may also be shifted.

[0155] In the embodiment shown in FIG. 9, a portion of the reflectingmirror is made into full reflecting prisms 108, 110 so that along withbeing able to align the optical path length for the R light, G light andB light, the back-focus can be shortened.

[0156] Errors in the assembly accuracy can be reduced by bonding thefull reflecting prism 108, the color combining prism and the polarizedbeam reflector 105RGB.

[0157] The light output from the G light liquid crystal display element107G is made into S polarized light and the light output from the Rlight liquid crystal display element 107R is made into P polarizedlight, and the B light output from the B light liquid crystal displayelement 107B is made into S polarized light so that the efficiency ofthe R, G, B light and the contrast rate can therefore be improved byusing the above structures.

[0158] In the embodiment of FIG. 11, after the light permeates throughthe designated wavelength converter element 112 d, and is colorseparated by the polarized beam splitter 111 constituting the colorseparating means, the first and second light colors are input and outputfrom the matching liquid crystal display element by way of the colorseparating/combining means (such as the polarized beam splitter 105RG),are combined in the color separating/combining means, are output from anintersecting optical axis separate from the input axis, and input to thecolor combining means by way of the mirror (full reflecting mirror 117).The third color is input and output to the liquid crystal displayelement matching the third light by way of the mirror (full reflectingmirror 108) and input to the color combining means. Afterwards, thefirst, second and third lights are combined by way of the colorcombining means. If a ½ wavelength plate is input to the location of thepolarizing plate 103, or the designated wavelength converter element112, the output directions of the first, second and third light can beoutput even if in directions parallel to or intersecting the opticalaxis of the lighting system.

[0159] In the embodiment of FIG. 12, the dichroic mirror 102 shown inFIG. 1 is substituted with the dichroic prism 111 b. This substitutionallows the effective length of the input light path up to the liquidcrystal display element to be shortened and the dispersion of the lightcan be suppressed. In particular if a condenser lens 119 such as shownfor example in FIG. 15 is inserted prior to the input to the dichroicprism 111 b, then when set to a telecentric system, the variations inthe optical ray angle for the polarizing plate and the dichroic mirror,dichroic prism, and polarized beam splitter can be suppressed to anabsolute minimum, and the adverse effects of prism inner surfacereflection due to light diffusion can be reduced.

[0160] As shown in the embodiment of FIG. 13, by aligning the prismsurfaces of the polarized beam splitter 111 and the polarized beamsplitter 105RGB, when the surfaces of the polarized beam splitter 111are aligned with the surfaces of the full reflecting mirror 108, theassembly accuracy is improved and accurate positioning is easy toachieve.

[0161] As shown in FIG. 14, when set to a telecentric system, changes inthe light ray angle can be kept to a minimum in the polarizing plate,dichroic prism, and polarized beam splitter, by inserting the condenserlenses 119 a, 119 b on each optical path, and the adverse effects ofprism inner surface reflection due to light diffusion can be reduced.

[0162] Also, by installing a condenser lens 119 prior to the first colorseparating means as shown in FIG. 15, when set to a telecentric system,changes in the light ray angle can be kept to a minimum in thepolarizing plate, dichroic prism, and polarized beam splitter, andadverse effects of prism inner surface reflection due to light diffusioncan be reduced.

[0163] In the embodiment of FIG. 8, the color alignment film 104 may forexample be a dielectric multilayer film vapor deposited on the directpolarized beam splitter or dichroic prism, and may be a color film or acolor filter such as of colored glass wherein a polarized beam splitteror a dichroic mirror is vapor deposited with a dielectric multilayerfilm on a glass plate or ½ wavelength plate, ¼ wavelength plate,designated wavelength converter element, or polarizing plate. What isessential is that any suitable material be capable of lowering thepermeance rate of the designated wavelength region.

[0164] In this embodiment, the full reflecting mirror 108 is not alwaysrequired and may be installed facing the output surface of the B lightof the color combining polarized beam splitter 105 RGB.

[0165] However, since the height of the optical path R, G, B light canbe aligned by installing the full reflecting prism 108 such as in thisembodiment, the irregularities in the color can be eliminated.

[0166] In this embodiment, the optical unit may be comprised of a colorseparating/combining means such as a color separator mirror 102 and apolarization beam splitter 105RG (or dichroic prism), a color combiningmeans such as a polarization beam splitter 105RGB (or dichroic prism),

[0167] so that R light, G light and B light color separation andcombining can therefore be achieved with a lightweight and low coststructure.

[0168] In FIG. 8, FIG. 10 and FIG. 14, the wavelength band can beselected to lower the wavelength of the light on the color alignmentfilm 104, and along with performing color alignment, satisfactory colorrestoration can be achieved. For example by selecting a wavelength tolower the permeance ratio in the color alignment film 104 a, 104 b, thepermeance rate in the cyan wavelength region and the yellow wavelengthregion can be lowered to achieve a satisfactory color. The yellowcomponents can be increased to make the image brighter. In such cases,the alignment film 104 can be adjusted to cut the cyan components sothat the white balance is maintained.

[0169] In the embodiment of FIG. 8, the color alignment film 104 a wasinstalled on the B light input surface of the polarizing beam splitter105RG but as shown in FIG. 10, the color alignment film 104 a may beinstalled on the output side of the B light polarizing beam splitter111. In FIG. 8, the color alignment film 104 b was installed on the Rlight and B light incident side of the (detecting) colorseparation/combining polarizing beam splitter 105RG but as shown in FIG.10, it may be installed on the output side of the R light and B light ofthe color separating/combining polarizing beam splitter 105RG, or may beinstalled on the incident side of the R light and B light of the colorseparating/combining polarizing beam splitter 105RG or dichroic prism.In other words, the same effect can be obtained whether the coloralignment film 104 is installed on the incident side (surface) or outputside (surface) of the dichroic prism or color combining side of the Rlight and B light of the color separating/combining polarizing beamsplitter or analyzing polarizing beam splitter.

[0170] In the embodiment of FIG. 9, color alignment can be performed byadjusting the dichroic mirror such as the color separator mirror 102 andthe designated wavelength converter elements 112 a, 112 b. However, thefollowing examples are applicable to other embodiments and not just theembodiment of FIG. 9.

[0171] The example for this case is described while referring to FIG.16.

[0172]FIGS. 16A and 16B are drawings showing the spectroscopiccharacteristics of the light permeance rate. The horizontal axis is thewavelength W and the vertical axis is the light output P. FIG. 16A showsthe output characteristic curve of the color separator mirror 102 ofFIG. 9, configured for example, so light from 500 nm to 600 nm does notpermeate through. Of the light permeating through the color separatingmirror 102, light within a wavelength S1 longer than a wavelength of 600nm is converted from S to P polarized light, and configures acharacteristic curve P1 of designated wavelength converter element 112 aso that S polarized light of wavelength greater than S` permeatesthrough as is. This light is reflected by the liquid crystal displayelements 107B, 107R and the polarized light converted, light of awavelength up to S1 is converted to S polarized light, light on awavelength of more than S1 is converted to P polarized light. As shownin FIG. 10C, the light below wavelength S2 is converted from P to Spolarized light, and the light above a wavelength S1 is not polarizedand when it permeates the designated wavelength converter element 112 bunchanged as P polarized light having the characteristics of line P2,the S polarized light of wavelength S2 through S1 is unchanged so thatthe light in this region is reflected by the polarized beam splitter105RG and is not therefore input to the projection lens. The light onthe wavelength S2 through S1 can in this way be cutoff.

[0173] In this way, by combining the reflective mirror 110 and thedesignated wavelength converter elements 112 a and 112 b, the permeancerate of the designated wavelength can be changed. In this embodiment,the yellow color can be eliminated by setting 600 nm to 580 nm.

[0174] In the same way, the brightness can be improved by changing thestructure of the designated wavelength converter element 112 and thecolor alignment film 104. If the objective for example is to improve thebrightness of a light ray, a half-value of color alignment film 104 anda half value of designated wavelength converter element 112 can becombined and light in the vicinity of 500 nm for example light from 500nm to 515 nm can be cut out, so that a light ray in the vicinity of 580nm can be input and the brightness improved and the white balance canalso be improved.

[0175] The same effect can also be obtained by combining the coloralignment mirror 104 and the dichroic mirror 102. In this embodiment thedichroic mirror 102 and the full reflecting mirror 110 can besubstituted with dichroic prisms.

[0176] Therefore in the above description, the dichroic mirror 102 andthe full reflecting mirror 110 can be substituted with dichroic prisms.

[0177] The polarizing plate 103 b is installed in the vicinity of thepolarized beam splitter 105RG in the embodiments of FIG. 8 and FIG. 9,and the polarizing plate 103 c is installed in the vicinity of thepolarized beam splitter 105RG. When these polarizing plates 103 areattached in the vicinity of the polarized beam splitter, the boundary isreduced, and the light permeance rate can be improved. The polarizedbeam splitter 105RG has a large heat radiating effect so that heat fromthe polarizing plate 103 is absorbed and the cooling ability of thepolarizing plate 103 is increased.

[0178] The optical units of FIG. 8 and FIG. 9 can be comprised ofdichroic prism. In this case, a polarizing plate 103 can be attached tothe dichroic prism. In such a case, the polarizing plate 103 ispreferably comprised of film.

[0179] In the embodiments of FIG. 8 and FIG. 9, when installing a coloralignment film on the incident side of the dichroic mirror such as acolor separator mirror 102, when performing for example vapor depositionof a dielectric multilayer film, when the film thickness is changed sothat the portions with a large light input angle are thick and portionswith a small light input angle are thin, a shift occurs in thewavelength value so that the color of the output light and variations inthe color can be adjusted.

[0180] When the optical units such as shown in FIG. 8 and FIG. 9 arecomprised of dichroic mirrors and dichroic prisms, in other words, whencomprised of dichroic prisms or dichroic mirrors such as colorseparation mirrors 102, and when a dichroic prism is installed insteadof the dichroic prism, the same effect can be obtained as when thethickness of a color alignment file is changed and installed on theseinput surfaces.

[0181] In the embodiments of FIG. 8 and FIG. 9, the glass material canpreferably be changed in the color separating/combining polarized beamsplitters 105RG, 105RB and polarized beam splitters 105RGB. A glassmaterial with a low birefringence (double refraction) such as PBH 53 forexample can be selected for polarized beam splitters 105RG, 105RB, andfor instance, a lightweight and low cost glass material can be selectedsuch as BK7 for the color combining polarized beam splitters 105RGB toachieve ideal performance, low cost and a low weight.

[0182] A structure wherein the color separator mirror 102 can be made tocomprise the dichroic prism and polarized beam splitter, and thepolarized beam splitter 105 can be substituted with a dichroic prism isalso applicable in the same way. In this case, the color separatingdichroic prism just the same as the color combining polarized beamsplitter or dichroic prism can also use lightweight, low cost glassmaterial.

[0183] In FIG. 8 and FIG. 9, when the volume of the polarized beamsplitters 105RG, 105RB is set to V1, the volume of the color combiningpolarized beam splitters 105RGB is set to V2, then V1 can be set smallerthan V2, and when a glass material as described above is utilized,performance can be optimized according to the usage characteristics, anda low cost glass material can be used, and the weight also reduced. As avariation on the structure, a dichroic mirror or a dichroic prism can beused as the color separator mirror 102, and a dichroic prism can also beused instead of the polarized beam splitter 105. When in particular, thesize of the color separating and color combining polarized beam splitter105 and dichroic prism is increased, eclipsing of the input/output lightbeam can be prevented. In this case, when the object is the permeanceratio of the glass material or the reflectance rate, the performance canbe improved, costs reduced and a glass material of a lighter specificgravity used to obtain a lighter weight by changing the glass materialof the polarized beam splitter 105 or dichroic prism. If the glassmaterial of the analyzing polarized beam splitter is highly refractive,with a light elasticity coefficient of 0.5×10−12N/m2, a size of □32, andthe stress is within 5.3×104 Pa, then the light extinction ratio issatisfactory, yet if the specific gravity of the color combining andcolor separating dichroic prism and polarized beam splitter is light,and if a glass material with a good overall permeance ratio alsoincluding the dielectric multilayer film is utilized, then goodperformance, lightweight and low cost can be obtained even when thevolume was increased to prevent eclipsing of the light rays.

[0184] Next, the case when installing the liquid crystal element in thepolarized beam splitter 105 is explained while referring to FIG. 17.

[0185]FIG. 17A and FIG. 17B are fragmentary cross sectional plan viewsshowing a the embodiment for installing the liquid crystal element inthe polarized beam splitter. In FIG. 17A, a liquid crystal material 132is filled into the frame 107 of the liquid crystal element 107G. A coverglass 133 a, 133 b is installed on both sides. After aligning theposition of the liquid crystal element 107G, the frame 130 is directlybonded to the polarized beam splitter 105G by the adhesive 134 a, 134 b.A UV adhesive solution or a heat hardening adhesive may also be utilizedas the adhesive for strength.

[0186] In this embodiment, the cover glass 133 a and the polarized beamsplitter 105G may be bonded with adhesive or clamped.

[0187] Another embodiment is shown in FIG. 17B installed with analignment plate 134. This alignment plate 134 is glued with bondingagent 134 to the polarized beam splitter 105G. After adjusting theposition of the liquid crystal element 107G relative to the polarizedbeam splitter 105G, the frame 130 is glued or clamped to the alignmentplate 134. Also, the air layer between the cover glass 133 a and thepolarized beam splitter 105G can be eliminated by filling with adhesiveor silicon oil.

[0188] The light utilization efficiency of this embodiment can beincreased by reducing the boundary between the polarized beam splitter105G and the liquid crystal element 107G.

[0189] The embodiment of FIG. 17 was explained using the polarized beamsplitter 105G and G light liquid crystal element however the same effectcan be achieved by directly installing an R light, B light liquidcrystal element 107R, 107B in the polarized beam splitter 105G.

[0190] Next, the assembly of the polarized beam splitter is describedutilizing FIG. 18.

[0191]FIG. 18A is a perspective view showing an embodiment of thepolarized beam splitter. FIG. 18B is a perspective view showing anembodiment of the assembly structure of the polarized beam splitter.This embodiment has a structure comprised of four prisms as the dichroicprisms or polarized beam splitter in addition to the color separatingmirror 102 and full reflecting mirror 110 shown in FIG. 8.

[0192] In FIG. 18A, the number 151 denotes a color separating polarizedbeam splitter or dichroic prism and is comprised of a tall triangularcolumn-shaped prism 151H and a short triangular column-shaped prism 151Lfor installing a step in the alignment surfaces. The numeral 152 denotesa G light polarized beam splitter, and is comprised of a tall triangularcolumn-shaped prism 152H and short triangular column-shaped prism 152Lfor installing a step in the alignment surfaces. The reference numeral153 is an R light and B light polarized beam splitter and is comprisedof a tall triangular column-shaped prism 153H and a short triangularcolumn-shaped prism 153L for installing a step in the alignmentsurfaces. The colors in the light are separated by the color separatingpolarized beam splitter or dichroic prism, and the G light is reflectedby the polarized beam splitter 152 or dichroic prism and input to the Glight liquid crystal element 107G. The G light reflected from the liquidcrystal element 107G is reflected by the color combining polarized beamsplitter 154 and input onto the projector lens (not shown in drawing).

[0193] The R light and B light separated in the polarized beam splitter151 are separated in the polarized beam splitter 153 and inputrespectively to the liquid crystal elements 107R, 107B. The R light andB light reflected by the liquid crystal elements 107R, 107B permeatesthe polarized beam splitter 154 and is input to the projector lens (notshown in drawing).

[0194] A polarizing plate, ½ wavelength plate, and designated wavelengthconverter element are inserted in the gap between each polarized beamsplitter. Steps 155 are respectively installed above and below thepolarized beam splitters 151-154 by means of the tall triangularcolumn-shaped prism and short triangular column-shaped prism assembly.In FIG. 18B, the reference numeral 157 is an assembly structure. Thestands 158H-161H are mounted with the long triangular prisms 151H-154Hand the stands 158L-161L are mounted with the short triangular prisms.The protrusion 163 mounted in the assembly structure piece 157 is usedfor positioning.

[0195] During assembly of the polarized beam splitter in the assemblystructure 157 as shown in FIG. 18A, the positioning protrusions 163 inthe stands 158H-161H are mounted to make contact with the bottom of thelong triangular prisms 151H-154H, and the positioning protrusions 163 inthe stands 158L-161L are mounted to make contact with the bottom of theshort triangular prisms 151L-154L. A groove is formed between each ofthe polarized beam splitters, and a polarizing plate and designatedwavelength converter element installed. The positioning precision can befurther improved at this time by installing springs or foam, etc.

[0196] In this embodiment, a step section was installed in the polarizedbeam splitters 151-154 and positioning performed by means of these stepsections so that the surface of the dielectric multilayer film of thepolarized beam splitter forms the reference surface, the assemblyprecision is improved and the performance therefore enhanced.

[0197] As can be clearly seen in the figure, in this embodiment thecolor separating beam splitter 151 widens the light input surface areaof the prism 151, and the output side of the polarized beam splitter orin other words, widens the output side surface area of the prism 154H ofthe color combining polarized beam splitter. The light permeance surfacearea is preferably made smaller as the light travels forward up to theliquid crystal display elements, and as the light from the liquidcrystal display elements travels forward, the light permeance surfacearea is preferably set larger to prevent eclipsing of the light. Aneffect of such kind can be achieved in this embodiment.

[0198] In FIG. 18, the same effect can of course be obtained by astructure comprising a portion of the polarized beam splitter with adichroic prism.

[0199] Next, the alignment mechanism of the ¼ wavelength plate isdescribed while referring to FIG. 19.

[0200]FIG. 19 is a side view for describing the installation of the ¼wavelength plate. In the figure, the reference numeral 160 is forexample an installation plate for the ¼ wavelength plate of FIG. 8, andis installed with a window for allowing light to permeate from thepolarized beam splitter 152. The ¼ wavelength plate 106 b is clamped tothe shaft 161. The shaft 161 is installed to allow rotation in theinstallation plate 160, and aligned so the light on the polarizedoptical axis matches the liquid crystal display element 107G, and isclamped after alignment to the installation plate 160. The center of therotation axis of the ¼ wavelength plate 106 b is positioned to match theupper edge of the prism 152L. In other words, the ¼ wavelength plate 106b is a reference for the upper edge or lower edge or output side orleft/right sides of the polarized beam splitter 152. Accordingly, thereference is also fixed during replacement of the liquid crystalelement, the alignment procedure is simple to perform since the originalposition is clear. Needless to say, the above example can also beapplied to installation of the ¼ wavelength plate.

[0201] The polarized beam splitters 105RG, 105RB, 105RGB in FIG. 8 andFIG. 9 have a surface that does not contribute to the permeance orreflection of light, however this surface is intended to prevent randomreflections from these surfaces. The surface not used for permeance orreflection of light is preferably made of non-transparent glass orpainted black. The same is in effect for substituting the polarized beamsplitter with a dichroic prism.

[0202] The B light input to the color combining polarized beam splitter105RGB is S polarized light as per FIG. 8, the RG light is P polarizedlight, and the optical axis of light output from the B light liquidcrystal display element 107B and optical axis of light output from thecolor combining polarized beam splitter 105RGB are installed so as tointersect one another. A dichroic mirror or dichroic prism may beutilized instead of the color combining polarized beam splitter 105RGB.

[0203] When using a dichroic mirror or dichroic prism instead of thecolor combining polarized beam splitter 105RGB shown in FIG. 8, the Spolarized light has good efficiency as light combined with other lightto serve as reflected light in the color combining dichroic mirror ordichroic prism, and conversely P polarized light has good efficiency ascombined light to serve as permeant light. In other words, when thereflected light is S polarized light, the reflectance band width of thedielectric film formed on the dichroic mirror or dichroic prism is wide,and there is little susceptibility to effects such as wavelength shiftdue to characteristics of the film. Further, when the permeant light isP polarized light, the permeance band width of the dielectric filmformed on the dichroic mirror or dichroic prism is wide, and there islittle susceptibility to effects such as wavelength shift due tocharacteristics of the film. Accordingly, the efficiency is good in astructure in which the B light is P polarized reflective light, the RGlight permeating the dichroic mirror or dichroic prism combines as Ppolarized light and is reflected by means of the dichroic mirror ordichroic prism and output along the optical axis.

[0204] When utilizing the color combining polarized beam splitter 105RGBon the other hand, the light from the B light liquid crystal displayelement 107B is reflected by the color combining polarized beam splitter105RGB, and when configured to combine with the RG light and be output,the reflected light is of course made into S polarized light and thepermeating light must be made into P polarized light.

[0205] In FIG. 9, the G light input to the color combining meansconsisting of the color combining polarized beam splitter 105RGB is Spolarized light, the RB light is P polarized light, and further theoptical axis for light output from the polarized beam splitter 105RGBconstituting the output means is installed so as to be in parallel withthe light output from the G light liquid crystal display element 107G.

[0206] Referring to FIG. 9 shows a structure in which the R light liquidcrystal display element 107R and the B light liquid crystal displayelement 107B are installed at right angles, and the input light axis andthe output light axis of the color separating polarized beam splitter105RB for separating the R light and the B light are at approximateright angles, and the projection lens 113 is installed to beapproximately in parallel with this output light axis.

[0207] Needless to say, in this embodiment, the dichroic mirror and thedichroic prism can be utilized instead of the color separating polarizedbeam splitter 105RB.

[0208] An image display device as shown in FIG. 14 can be obtained bymeans of the structure shown for the optical unit of FIG. 8 and FIG. 9.

[0209]FIG. 20 is an overall perspective view showing an embodiment ofthe image display device of the invention. This figure is shown asviewed as an optical system. In the figure, the reference numeral 171 isthe optical system, reference numeral 172 is the optical unit as shownin FIG. 8 and FIG. 9, the optical axis of the light input to theseparating unit 172 from the optical system 171 is bent at a right angleand output from the separating/combining unit 172. This light isreflected by the reflecting mirror 172 installed on the rear side of thecabinet and projected onto the screen 175 by way of the projecting lens118. In this case, the optical axis of the separating/combining unit 172and the projection lens 118 may be shifted and the input angle changedto the reflecting mirror 172 on the rear side of the cabinet.

[0210] The above structure allows the mirror size to be reduced and thesize of the set depth wise to be reduced. In this case, the optical axisof the color combination prism and analyzing light prism may be shifted.Further, the optical axis of the projection lens 118 and the opticalaxis of the color combining prism may be shifted in steps.

[0211]FIG. 21 is a perspective view showing another embodiment of theoptical system. This figure differs from the embodiment of FIG. 14 inthat a mirror 176 is installed for converting the optical axis. Byinstalling the mirror 176 in this embodiment, the image can be directlyprojected onto the screen.

[0212] In the embodiments of FIG. 20 and FIG. 21, the optical system canbe compactly installed.

[0213] In FIG. 8, the R light, B light and G light is input from thedirect polarity converter element 101 to the reflective mirror 109, andthe G light and B light permeated through the reflective mirror 109, andthe B light reflected. This B light is reflected at the polarized beamsplitter and input to the B light liquid crystal element. The light fromthe B light liquid crystal display element is input to the colorcombining polarized beam splitter 105RGB, permeated through it andoutput. The G light and R light on the other hand, is input to therespective R light and BG light liquid crystal elements. The lightoutput from these light liquid crystal elements is reflected isreflected at the color combining polarized beam splitter 105RGB, andthen output so that the optical axis for light input to the mirror 109functioning as the color separating mirror is approximately in parallelwith the optical axis for inputting light onto the projection lens fromthe color combining polarized beam splitter 105RGB. In this case, thefact that the polarized beam splitter can be substituted with thedichroic mirror and dichroic prism is readily apparent to one skilled inthe related art.

[0214] An image display device utilizing the above described opticalunit is next described while referring to FIG. 22.

[0215]FIG. 22 is an overall perspective view showing another embodimentof the image display device of the invention. In the figure, the inputaxis for light input to the optical unit 178 from the optical system 171is approximately in parallel with the optical axis of light output fromthe optical unit 178. The light output from the optical unit 178 isreflected at the reflection mirror 179 and input to the projection lens118, and reflected at the reflection mirror 174 installed at the rearside of the cabinet 173 and projected onto the screen 175.

[0216] The back-focus of the projection lens can be shortened in thisembodiment so that the number of projection lenses can be reduced andthe structure made more compact.

[0217]FIG. 23 is a perspective view showing still another embodiment ofthe optical system. The figure shows a component placement not utilizingthe reflection mirror 179. Compared to the embodiment of FIG. 22, theimage display device is somewhat longer vertically but can be shortenedhorizontally.

[0218] In FIG. 20 and FIG. 21, when the light output from the projectionlens is projected onto the screen 175 by means of the reflective mirror174 installed on the rear side of the cabinet 173, the lens, is forexample a full panel lens integrated with the screen 175 and can beinstalled to project the light approximately in parallel and achieve acompact set structure.

[0219] In FIG. 1, the condenser lens 30 installed upstream of the liquidcrystal display elements 2R, 2G, and 2B can be integrated with theprojection lens 20 and when configured so that a first composite focuspoint position is present in the vicinity of the aperture of theprojection lens 20, the light ray passing through the polarized beamsplitters 16G, 16RB and color combining mirror 19 can be focused so thatthese components can be a compact structure. In particular, whenutilizing a color combining polarized beam splitter or dichroic prisminstead of the color combining mirror 19, the prism becomes lighter anda lower cost can be obtained.

[0220] In FIG. 8 and FIG. 9, when a dichroic prism or dichroic mirror isutilized instead of the color separating mirror 102, and a dichroicprism or dichroic mirror is utilized instead of the polarized beamsplitter 105RGB, unnecessary light can be eliminated and color puritycan be improved by setting the half wavelength of the color separatingdichroic prism or dichroic mirror to a different value to the halfwavelength of the color combining dichroic prism or dichroic mirror. Forexample, when the input dichroic characteristics, or in other words whenthe reduced half wavelength of the bandpass filter is specified as 500nm, the high region half wavelength is specified as 590 nm, the reducedhalf wavelength for dichroic characteristics of the output prism isspecified as 510 nm, and a high region half wavelength of 580 nm isspecified, then the cyan between 500 nm and 510 nm, and the yellow lightbetween 580 nm and 590 nm can be eliminated. This combination can alsobe achieved with a dichroic mirror and designated wavelength converterelement. This combination is also possible with a designated wavelengthconverter element and polarized beam splitter. A combination cuttinglight in the near ultraviolet or near infrared region light is alsopossible.

[0221] In the embodiments of FIG. 8 and FIG. 9, when a cooling path isinstalled between the polarized beam splitter 105RG or 105RB andpolarized beam splitter 105RGB, cooling efficiency is satisfactorybecause the designated wavelength converter element 112 and polarizingplate can be directly cooled.

[0222] The designated wavelength converter element 112 and polarizingplate 103 can be directly cooled by installing a blow vent for a coolingmedium on the light input surface of the polarized beam splitter 105RGor polarized beam splitter RB and polarized beam splitter 105RGB orbetween the polarized beam splitter 105RG or polarized beam splitter RBand polarized beam splitter 105RGB.

[0223] Cooling efficiency be even further improved by installinginput/output vents on the light input surface of the polarized beamsplitter 105RG or polarized beam splitter RB and polarized beam splitter105RGB or between the polarized beam splitter 105RG or polarized beamsplitter RB and polarized beam splitter 105RGB, and by increasing thecoolant medium flow rate.

[0224] The polarizing plate 103 can be directly cooled, highly efficientcooling medium achieved and performance improved by directly cooling thepolarizing plate 103 installed at the light input surface of thepolarized beam splitter 105RG or polarized beam splitter RB andpolarized beam splitter 105RGB or between the polarized beam splitter105RG or polarized beam splitter RB and polarized beam splitter 105RGB.

[0225] The invention along with having a compact and lightweightstructure, also allows freely controlling the color purity, andimproving color irregularities and simultaneously improves performance.By further combining a polarized beam splitter and designated wavelengthconverter element as a color separating means, the effects due to angledependency are slight and planning the color performance is easilyaccomplished.

[0226] A compact, high brightness, high image quality optical unit orprojection type image display device can therefore be achieved. A lowcost is further achieved since the number of parts can be reduced.

[0227]FIG. 24 is an upper concept view of another embodiment of theliquid crystal projector optical system of the invention.

[0228] A graph of rotation characteristics of polarized light of thepolarized rotator elements 219 and 261 for only the B light wavelengthis used in the embodiment in FIG. 25. The horizontal axis on the graphshows the light wavelength, and the vertical axis shows the polarizedlight rotation angle. As shown in FIG. 25, the polarized rotatorelements in this embodiment have an intermediate point for rotating thepolarized light to a position with a wavelength of approximately 550 nm.

[0229] Another embodiment of the invention is described in detailutilizing FIG. 24.

[0230] the white colored light radiated from the light source 201 isconverted by the reflector to an approximately parallel light beam 202.The parallel light beam 202 is comprised of R light components 202R, Glight components 202G and B light components 202B. The parallel lightbeam 202 is converted to S polarized light by the polarity converterelement 203 and becomes S polarized R light 204R, S polarized G light204G, and S polarized G light 204B.

[0231] The S polarized R light 204R and S polarized B light 204B inputto the reflecting RB dichroic mirror 205 and after permeating throughthe surface of the dichroic mirror, permeates the polarizing plate 207and P polarity light components are absorbed, and the light becomes Spolarized R light 208R and S polarized B light 208B. The reason forinstalling the polarizing plate 207 at this position is becauserectification of polarized light by the polarity converter element 203is insufficient, and the image contrast suffers deterioration due tosome P polarized light contained in the 204R, 204G and 204B input light.A high contrast can be obtained by absorbing the P polarized light usingthe polarizing plate 207.

[0232] The S polarized R light 208R and S polarized B light 208B areinput to the polarity rotator element 209 for rotating the polarized Blight, the S polarized R light is not converted and becomes S polarizedR light 210R, the S polarized B light is rotated and becomes P polarizedB light 210B. The S polarized R light 210R input to the polarized beamsplitter prism 211 is reflected by the surface of the splitter 211 a,becomes S polarized R light 212R, and is in put to the reflecting liquidcrystal display element 213R. Here, the light to brighten the display bythe liquid crystal display element 213R is reflected as P polarized Rlight 214R, and is reflected unchanged as S polarized R light to darkenthe display. The light when darkening the display is omitted along withR, G, and B in FIG. 24. The P polarized R light 214R is input again tothe polarized beam splitter prism 211, and this time permeates thesplitter surface 211 a as P polarized light and becomes P polarized Rlight 215R.

[0233] The P polarized B light 210B on the other hand, permeating thepolarity rotator element 209 for rotating the polarized B light, isinput to the polarized beam splitter prism 211, permeate the splittersurface 211 a and becomes S polarized B light 212, and is input to thereflecting liquid crystal display element 213B. Here, the light tobrighten the display by the liquid crystal display element 213B isreflected as S polarized B light 214B, and the light to darken thedisplay is reflected unchanged as P polarized B light. The light tobrighten the display is S polarized B light 214B and is input again tothe polarized beam splitter 211, and this time is S polarized light sothat it is reflected by the splitter surface 211 a, and becomes Spolarized B light 215B, and combined with the P polarized R light 215R.

[0234] The P polarized R light 215R and S polarized B light 215B isinput to the polarity rotator element 216 for rotating the polarized Blight, the P polarized R light 215R becomes P polarized R light 219Rwithout being changed. The S polarized B light 215B is rotated andbecomes P polarized B light 219B. Both of the P polarized R and B lightthat became P polarized R light 219R and P polarized B light 219B areinput to the polarized beam splitter 220, and permeate the splittersurface 220 a, and become P polarized R light 221R and P polarized Rlight 221B. Also at this time, the S polarized R and B light fordarkening the display is reflected so that the contrast is furtherimproved in the R and B light.

[0235] The light 2G output from the light source 201 is converted to Spolarized G light 204G by the polarized converter element 203 and thenreflected by the G-reflecting RB dichroic mirror 205, input to thepolarizing plate 225, the P polarized light components are nearlycompletely cut out, the light becomes S polarized G light 226B and isinput to the polarized beam splitter 227. The S polarized G light 226Bis reflected in the polarized beam splitter surface 227 a and become Spolarized G light 228G and is input to the G-reflecting liquid crystaldisplay element 229G. Here, the P polarized G light to brighten thedisplay is reflected as P polarized G light 230G and again input to thepolarized beam splitter 227, this time as P polarized light so that itpermeates the splitter surface 227 a and becomes P polarized G light231G. The P polarized G light 231G is input here to the polarity rotatorelement 234, the polarized light rotated and becomes S polarized G light235G.

[0236] The S polarized G light 235G is here input to the polarized beamsplitter 220 and is reflected by the splitter surface 22 a and become Spolarized G light 236G, and is combined with the P polarized R light221R and S polarized B light 221B. The combined image light here has Ppolarized R and B light components, and S polarized G components, and isprojected, enlarged onto the projection lens 224.

[0237] In this embodiment, the upper and lower surfaces of each prismare painted a black color, serving to reduce internal reflections in thepolarized beam splitter or dichroic mirror prism and allows a highcontrast to be obtained.

[0238] In this embodiment, in regards to image contrast characteristics,the G image light 231G reflected by the G-reflecting liquid crystaldisplay element 229G is sufficiently reflected by the splitter surface227 a of the polarized beam splitter 127 as light for darkening thedisplay and so has high contrast. The R image light for darkening thedisplay is reflected at the splitter surfaces 211 a, 220 a of thepolarized beam splitter prisms 211, 220, and good contrast can beobtained. A high contrast can be obtained per the B image light from thesplitter surface 220 a of the polarized beam splitter prisms 220.

[0239] In this embodiment, even with characteristics such as shown inFIG. 25 for the polarity rotator elements 209, 216 for rotating thepolarized B light, the permeating B light and R light does not includelight wavelengths for angle rotation in an excess region so there islittle elliptical polarized light after permeation, and after permeatingthe polarizing plate 218, a high contrast can be obtained. By furtherutilizing the polarity rotator element 216 for improving the imagecontrast, there is no need to cut out light between the R and G light,and G and B light, so that light utilization efficiency is high.

[0240] Also in this embodiment, the distance from the polarity converterelement 203 to the reflective liquid crystal display elements 213R,229G, 213B can be made nearly equal so that the image has fewirregularities. Also the distance from the polarity converter element203 to the reflecting liquid crystal display elements, and the distancefrom the reflecting liquid crystal display elements to the projectionlens 224 can be increased 2.5 times in length along the sides of all theliquid crystal display elements, and the shortening of the projectionlens back-focus, an optical system that is compact and light-weight canbe achieved while simultaneously improving the light utilizationefficiency.

[0241]FIG. 26 is an overall upper view showing another embodiment of theliquid crystal projection optical system of the invention. In thisembodiment, in contrast to the above described embodiment, the polarityconverter element 216 on the optical path of the R and B image light isremoved, and the polarized beam splitter 220 is replaced with a dichroicmirror prism 239. The dichroic mirror surface 239 a of the dichroicmirror prism 239 is a multilayer thin film having properties to reflectthe G light wavelength and allow permeation of light on R and Bwavelengths.

[0242] The processing of the R light and B light of the optical systemin this embodiment is the same as the previous embodiment from theoutput from polarized beam splitter 211.

[0243] The P polarized R light 215R and S polarized B light 215Bcombined in the polarized beam splitter 211 are input to the polarityrotation element 216 for rotating the polarized B light, the P polarizedR light 215R becomes P polarized R light 219R without being changed. Thelight polarity of the S polarized B light 215B is rotated and it becomesP polarized B light 219B. The P polarized R light 219R and the Ppolarized B light 219B are input to the dichroic prism 239, permeate thedichotic surface 239 a, and become P polarized R light 241R and Ppolarized B light 241B. Also at this time, the S polarized light isreflected for darkening both the B and R light display so that thecontrast of both the R and B light is improved.

[0244] The processing of the G image light 231G is the same as in thefirst embodiment from output from the polarized beam splitter 227 andafterwards is input to the dichroic mirror prism 239.

[0245] The P polarized G image light 231G input to the dichroic mirrorprism 239 is reflected by the dichroic mirror surface 239 a and becomesP polarized G light 241G, and is combined with the P polarized R light241R and P polarized B light. The combined image light holds P polarizedlight components for both R, G and B and is projected as an enlargedimage onto the screen by the projection lens 224.

[0246] In this embodiment, besides obtaining the same effect as theother embodiments, the polarity rotator element 234 can be eliminatedand a more simple structure obtained.

[0247] In this embodiment, the same effect can be achieved by replacingthe dichroic mirror prism 39 with a dichroic mirror. Also, a dichroicfilm such as a sloping film can be freely set in the dichroic mirror 5,and combining dichroic mirror prism or dichroic mirror so that an imagewith high uniform color purity can be obtained.

[0248]FIG. 27 is an overall plan view showing a nineteenth embodiment ofthe liquid crystal projector optical system of the invention.

[0249] Compared to the embodiment of FIG. 26 of this invention, in thisembodiment the positions of the R and B liquid crystal display elements213R, 213B are interchanged, and the polarizing plate 207 for the R andB light input surface is changed to a polarizing plate 246 for B lightonly, and the polarity rotator elements 209, 216 for rotating thepolarity of the B light, are changed to polarity rotator elements 242,243 for rotating the polarity of the R light.

[0250]FIG. 28 is a graph showing the wavelength permeancecharacteristics of the polarizing plate for all wavelengths and thewavelength permeance characteristics of the polarizing plate only forthe B wavelength used in the embodiment of the invention. The B lightpolarizing plate used in this embodiment as shown in FIG. 28 functionson B light wavelengths but allows R light to permeate through on boththe absorption axis and permeance axis and does not function as apolarizing plate.

[0251] The effect of the optical system of this embodiment on the Rlight and B light is the same as the embodiment of FIG. 27 prior tolight input to the B only polarizing plate 246 and after light was inputto the dichroic prism 239.

[0252] The S polarized B light 204B that permeated the G-reflectingdichroic mirror 205 has its P polarized components absorbed by the Blight polarizing plate 246 and becomes S polarized B light 208B. The Spolarized B light 208B permeates through the polarity rotator element242 used for rotating the deflection of the R light, and becomes Spolarized B light 210B, and is input to the polarized beam splitterprism 211. The S polarized B light 210B reflected by the splittersurface 211 a of the polarized beam splitter 211 becomes S polarized Blight 212B, and is input to the B-reflecting liquid crystal displayelement 213B. When the B light reflected by the liquid crystal displayelement 213B is for brightening the display, the light becomes Ppolarized B light 214B, and is once again input to the polarized beamsplitter 211. The P polarized B light 214B permeates the splittersurface 211 a. In this case, the S polarized light to darken the displayis reflected by the splitter surface 211 a so that the B image light canhave a high contrast. Here, the P polarized B light 214B permeates thepolarity rotator element 42 for rotating the polarity of the R light,and becomes P polarized B light 217B and is input to the dichroic mirrorprism 239.

[0253] The S polarized R light 204R that permeated the G-reflectingdichroic mirror 205, permeates the B light polarizing plate 246, andpermeates the polarity rotator element 242 for rotating the polarity ofthe R light, and becomes P polarized R light 210R, and is input to thepolarized beam splitter 211. The P polarized R light 21DR permeatesthrough the splitter surface 211 a but in this case the S polarized Rlight components are reflected by the splitter surface 211 a, and the Ppolarized R light 212R having almost no S polarized components, and isinput to the R liquid crystal display element 213B. When the R imagelight reflected by the R-reflecting liquid crystal display element 213is brightening the display, it becomes S polarized light 214R, and isonce again input to the polarized beam splitter 211. The S polarizedlight 214R reflected by the splitter surface 211 a is input to thepolarity rotator element 243 use for rotating the polarity of the Rlight, and becomes the P polarized R light 217R, and is input to thedichroic mirror prism 239. In the R image light input to the dichroicprism 239, the S polarized light for darkening the display is reflectedby the dichroic surface 239, and becomes a P polarized R light 221Rhaving high contrast and is output to the dichroic prism 239.

[0254] The processing of the G light in the optical system of thisembodiment is the nearly the same as the embodiment of FIG. 26.

[0255] This embodiment, along with obtaining the same effect as theembodiment of FIG. 26, can utilize the polarizing plate on the input ofthe R, B light incident side as a B only polarizing plate, and higherbrightness therefore can be achieved.

[0256]FIG. 29 is an overall plan view of the liquid crystal projectoroptical system of another embodiment of this invention.

[0257] The embodiment of FIG. 29, in contrast to the embodiment of FIG.24 has a mutually aligned polarized beam splitter 211 and polarityrotator element 216 and polarized beam splitter prism 220 and polarityrotator element 234 and polarized beam splitter 227.

[0258] The processing of the R, G, B light in the optical system of thisembodiment is the nearly the same as the embodiment of FIG. 24.

[0259] In this embodiment the size of the polarized beam splitters 211,227 is smaller than the polarized beam splitter 220. The image lightoutput from the reflecting liquid crystal display element will thereforenot be eclipsed on the prism side and the overall structure of theoptical system can be made more compact.

[0260] Also in this embodiment, an angle bevel 249 is installed in anoptical element 220 such as a polarized beam splitter prism, and asupport section installed here, or by installing a support section foran optical member such as the polarized plate 207, 225 or the dichroicmirror 205 the positioning and the holding of the optical member can beeasily accomplished and the assembly time shortened during productionand further, the overall cost for the projection type image displaydevice can be reduced.

[0261] This embodiment, along with obtaining the same effect as theembodiment of FIG. 24, can achieve a compact structure for the overalloptical system, shorten the assembly time during production and alsoreduce the overall cost for the projection type image display device.

[0262]FIG. 30 is an overall plan view of the liquid crystal projectoroptical system of another embodiment of this invention.

[0263] The embodiment of FIG. 30 is a reflective three-plate liquidcrystal projector device having liquid crystal display elements 2R, 2G,2B corresponding to the three primary colors, R (red), G (green) and B(blue).

[0264] The fifth embodiment of the invention is hereafter described indetail while referring to FIG. 30.

[0265] The light source 201 is a white color lamp such as an ultra highvoltage mercury lamp, metal halide lamp, xenon lamp, mercury xenon lampor halogen lamp, etc.

[0266] The, light emitted from the lamp of the light source 201 isconverted to an approximately parallel light beam by a reflector 1 ahaving an elliptical surface, or a radial surface or a non-sphericalsurface, and input to a first array lens 250. The first array lens 250is comprised by a plurality of condensing lenses installed in arectangular frame having a size equivalent to the output beam apertureof this reflector 1 a and the light concentrated to form a plurality ofsecondary light source images on the second array lens 251. The secondarray lens 251 has an external shape with a size equivalent to the firstarray lens and is comprised of the same number of focusing lenses, andis installed in the vicinity formed by the plurality of secondary lightsource images. The individual focusing lenses of the second array lens251 have the effect of coalescing an image of the individual lenses ofthe first array lens 250 onto the liquid crystal display elements 213R,229G, 213B.

[0267] The white-colored light that permeated the second array lens 251is input to a row of diamond-shaped prisms of about half the size ofeach lens width installed for an appropriate pitch laterally along theoptical axis of each lens of the second array lens 251. A polarized beamsplitter 252 film is coated on the surface of these prisms and the inputlight is separated into P polarized light and S polarized light by thepolarized beam splitter 252. The P polarized light proceeds directlythrough the interior of the polarized beam splitter 252 and itspolarization direction is rotated 90 degrees by a polarity rotatorelement 253 installed on the output surface of this prism, becomes Spolarized light and is output. The S polarized light on the other hand,is reflected by the polarized beam splitter 252, and after beingreflected once more a long the basic direction of the optical axiswithin the adjoining diamond-shaped prism, is output as S polarizedlight.

[0268] The light is converted to light having S polarized light by thediamond-shaped prism and the polarity rotator element 253.

[0269] In the projection type image display device using the reflectiveliquid crystal display elements of the related art, the polarized lightis reflected in only one direction of the S polarized light or Ppolarized light due to the combination of input light polarizing plateand reflective liquid crystal display elements, so that only about halfthe reflected light amount is obtained. However, by using the polarizedbeam splitter 252 and the polarity rotator element 253, a projectionliquid crystal display device having twice the brightness of the deviceof the related art can theoretically be obtained by aligning along thedirection of the random polarized light emitted from the light source201 and inputting the light onto the reflective liquid crystal displayelement 213.

[0270] The first and second array lenses 250, 251 separate the lightoutput from the reflector 201 a in the first array lens, and by usingthe second array lens 251 to overlap the individual array images onceagain on the liquid crystal display element 213, a uniform image qualitywithout variations in brightness can be obtained at the center and thesides of the screen.

[0271] The S polarized light components of the light output from thepolarized beam splitter 252 are input to the condenser lens 254. Thecondenser lens 254 is comprised of one or a plurality of lenses, has apositive refractive potential, and has the effect of furtherconcentrating the light. The light permeating through the condenser lens254 is bent along the direction of its optical axis by the mirrors 255,256, and input to the condenser lens 257. The condenser lens 257 setsthe input angle for the polarized beam splitter of the chief ray inputnearly perpendicular to the reflecting liquid crystal display element213, and reduces irregularities caused by angular dependency of thepolarized beam splitter prism.

[0272] The light is next input to the G permeating RB reflectivedichroic mirror 258. In this embodiment, the G permeating RB reflectivedichroic mirror 258 has the same effect as even a dichroic mirror prism.The light is here separated into two portions: G light and R, B light bythe G permeating RB reflective dichroic mirror 258, and after permeatingthe respective polarizing plates 225, 207, is input to the angularpolarized beam splitters 227, 211. The G light proceeds and is input tothe G polarized beam splitter 227.

[0273] The input light at this time is S polarized light so is reflectedby the reflecting surface of the polarized beam splitter, and input tothe G reflecting liquid crystal display element 229G. The B light and Rlight permeates the polarizing plate 207 and then permeates the polarityrotator element 209 for rotating the polarization direction only of theB wavelength light, and is converted from S polarized light to Ppolarized light , and input to the R, B (exclusive) polarized beamsplitter prism 211. Here, the B light proceeds through the R, B(exclusive) polarized beam splitter prism 211 and is input to the Breflecting liquid crystal display element 213B. The S polarized R lighton the other hand stays unchanged, and after being reflected by thereflecting surface of the R, B (exclusive) polarized beam splitter prism211, is input to the reflecting liquid crystal display element 213R.

[0274] The above description is of course only one example and theinvention is not limited by this example. A configuration may beutilized wherein the positions of the R and B reflecting liquid crystaldisplay elements 213R, 213B are interchanged. Alternatively, thepositions of the R and B reflecting liquid crystal display elements213R, 213B and the polarized beam splitter 211, and the G reflectingliquid crystal display element 29G and the polarized beam splitter 227may be interchanged, etc. This embodiment obtains the same effects evenwhen incorporating the above changes.

[0275] After input of the light, the polarized light is converted torotated image light according the video signal for each reflectingliquid crystal display element color, and input once again to thepolarized beam splitter 211, 227 for each color and the S polarizedlight reflected and the P polarized light allowed to permeate through.

[0276] A plurality of reflective liquid crystal display elements 213R,239G, 213B are installed to correspond to the number of display pixels(for example, 1024 horizontal pixels and 768 vertical pixels for each ofthe three colors, etc.). The light polarization rotation angle of thepixels for the reflecting liquid crystal display elements changesaccording to an external drive signal, a light is reflected in adirection intersecting the polarization direction of the input light forbrightening the screen, and the image light is output towards theprojector lens 224 by the polarized beam splitters 211, 227. Whendarkening the display, the reflected light is in the same direction asthe polarized light, and the light returns as is, along the light inputpath, to the light source side.

[0277] The RGB light constituting the image is afterwards recombined bya color combining mirror such as the G-permeating RB reflective dichroicmirror prism 259, and the light passed through a projection lens 224such as a zoom lens and then arrives on the screen. The image formed bythe reflective liquid crystal display elements 213R, 229G, 213B is shownas an enlarged projection image on the screen by the projection lens224. The reflective liquid crystal display devices utilizing these threereflective liquid crystal display elements drives the lamp and the panelby means of a power supply 260.

[0278] Accordingly, the structure of this invention utilizing two unitsconstituted by a G exclusive and a R-B exclusive polarized beamsplitter, along with achieving a device with a compact and light-weightstructure, also allows freely controlling the color purity, improvescolor irregularities and simultaneously improves performance. Aprojection type image display device, compact and with high brightnessand high image quality can therefore be provided.

[0279] The projection type image display device of the invention has astructure wherein a dielectric multilayer film allows only a designatedlight wavelength from the input light to pass through, for input to thepolarized beam splitter installed approximately upstream of thereflective liquid crystal display element in order to obtain a peakvalue permeance rate or reflection efficiency of that P polarized light,and peak value of permeance rate or reflection efficiency for that Spolarized light that is input. A G exclusive beam splitter 227, forexample, is coated with a dielectric multilayer film ideal for G lightexclusively for a wavelength band in the vicinity from 500 nm to 600 nmcan be utilized, and also two R-B exclusive polarized beam splitter 211coated with a dielectric multilayer film ideal for R light and B lightexclusively for the two wavelength bands in the vicinity from 400 nm to500 nm and from the vicinity of 600 nm to 700 nm can be utilized whereinthe dielectric multilayer film is easily formed, and the permeance rateand reflecting efficiency are even further improved compared to therelated art. A reflective liquid crystal display device achieving bothhigh accuracy color restoration and high luminance, along with highefficiency contrast can therefore be provided. By also adding aninclined (sloping) film to the dichroic film, an image of higheruniformity and high color purity can be provided.

[0280] Since the projection type image display device of the invention,has a structure wherein after separating the light into G light and R, Blight, and wherein the polarizing plates 225, 207 are installed prior toinput of light to the polarized beam splitter prisms 211, 227, thedichroic filters 261, 262 or a color filter can easily be installed tocorrect the color 103 purity of the G light and R light on the lightinput surface of the polarizing plate, and both high monochrome colorpurity and high light utilization efficiency can be achieved.

[0281]FIG. 31 is an overall plan view of the liquid crystal projectoroptical system of another embodiment of the invention. Compared to theembodiment of FIG. 30 having one condenser lens 256, this embodiment hasthree condenser lenses 263R, 263G, 263B, installed at positions betweenthe reflective liquid crystal display element 213 and the polarized beamsplitters 227 and 211. The dichroic thing film of the color separatingdichroic mirror is an inclined (sloping) thin film.

[0282] In this embodiment, the reflective liquid crystal displayelements 213 and the condenser lens 263 are integrated together, howeverif installed separately, or if the front and rear of the condenserlenses 263 are reversed and integrated with the polarized beam splitters227 and 211 then the same effect can still be obtained.

[0283] The processing of the R, G, B light in the optical system of thisembodiment is the nearly the same as the embodiment of FIG. 30. Also, bysetting the condenser lens position just upstream of the reflectiveliquid crystal display elements, the internal surface reflection withinthe dichroic prism 259 and the polarized beam splitters 227 and 211becomes slight, and a structure having high image quality and highcontrast can be obtained.

[0284] Also in this embodiment, the angle of the chief ray input to thedichroic mirror for lighting the sides of the screen may sometimes notbe parallel with the chief ray on the center of the screen, so thatcolor variations are prone to occur on the left and right of the screenimage however by making the dichroic film an inclined (sloping) film, animage with few color variations can be obtained.

[0285] Also in this embodiment, a first composite focus point of thecondenser lens 263 is present in the vicinity of the constrictingsurface of the projection lens 224, and the center axis of the condenserlens 263 is aligned with the center of the reflective liquid crystaldisplay element 213, and further, the center axis of the projection lens224 is offset upwards to the panel center so the projected image iscenter-offset upwards to the projector,-and therefore a satisfactoryimage having few brightness variations between the center and sides ofthe image can be obtained.

[0286]FIG. 32 is an overall plan view of the liquid crystal projectoroptical system of another embodiment of this invention. In contrast tothe embodiment of FIG. 6, the embodiment of FIG. 32 is installed with acondenser lens 264 and further the focal distance combined for thecondenser lens 265 and the condenser lens 264 is set nearly the same asthe condenser lens 263 in the above embodiment.

[0287] The processing of the R, G, B light in the optical system of thisembodiment is the nearly the same as the embodiment of FIG. 31. Also, byseparating the condenser lens into two lenses, the effect can beobtained that a condenser lens 265 with smaller power can be designed,and deterioration in the image focus can be reduced. The angle of thechief ray permeating the polarized beam splitters 227 and 211 can bemade even smaller so that the occurrence of color irregularities can befurther reduced.

[0288] This invention can therefore be made compact and lightweight andperformance can be improved.

What is claimed is:
 1. An image display device comprising, a reflectiveimage display element for forming an optical image according to a videosignal from light output from a light source unit, and an optical systemto beam the light onto the reflective image display element and combineand output the light reflected from the reflective image displayelement, wherein the image display device is installed with a colorseparating means for separating the input light into a plurality oflight, and a color separating/combining means and color combining meansinstalled on the optical axis of the light separated from the colorseparating means.
 2. An image display device according to claim 1,wherein a first reflecting means and a second reflecting means areinstalled, and one light portion separated by the color separating meansis reflected by the first reflecting means and input to the colorseparating/combining means, and the other light portion separated by thecolor separating means is reflected by the second reflecting means andthen input to the color combining means.
 3. An image display devicecomprising a color separating means to separate light into a first lightand a second light and a third light, a color separating/combining meansto separate and combine the first light and the second light, a firstand second liquid crystal display element installed at approximate rightangles in the vicinity of the color separating/combining means, a thirdliquid crystal display element to input the third light, and colorcombining means to respectively combine the first, the second and thethird light separated by the color separating means, wherein the firstand second light separated by the color separating means arerespectively input to the first and second liquid crystal displayelements, and the first light and second light output from the firstliquid crystal display element and the second liquid crystal displayelement are combined in the color separating/combining means, and thefirst light and second light output from the color separating/combiningmeans are input to the color combining means, and the third lightseparated by the color separating means are input to the third liquidcrystal display element, and the light output from the third liquidcrystal display element is input to the color combining means, and thefirst light and the second light and the third light are combined.
 4. Animage display device according to claim 3, wherein a first reflectingmeans is installed along the optical path from the color separatingmeans to the color combining means on the optical axis of the first andsecond light.
 5. An image display device according to claim 4, wherein asecond reflecting means is installed along the optical path from thecolor separating means to the third crystal display element on theoptical axis of the third light.
 6. An image display device according toclaim 3, wherein a first designated wavelength converter element forconverting the polarization direction of a first light is installed onthe incident side of the color combining/separating means, a seconddesignated wavelength converter element for converting the polarizationdirection of a second light is installed output side of the colorcombining/separating means, and a polarity converter element isinstalled on the optical path from the color separator means to thethird image display element on the third optical axis.
 7. An imagedisplay device according to claim 5, wherein the reflecting means iscomprised of any of aluminum, silver vapor deposition mirrors, fullreflective prisms and mirror vapor deposition prisms, or is comprised ofany of dichroic mirrors and dichroic prisms.
 8. An image display devicecomprising: a color separating means for separating color in the light,a first reflecting means to change the optical axis of one light portionfrom the color separating means to an approximate right angle; a colorseparating/combining means to separate a light input by reflection fromthe first reflecting means into a first light and a second light, inputthe light into a first and a second liquid crystal display elementinstalled in the vicinity, and combine the first light and the secondlight output from the first liquid crystal display element and secondliquid crystal display element; a color combining means to be input witha first light and a second light from the color separating/combiningmeans; and a second reflecting means to reflect the third lightseparated by the color separating means after permeation, and input thethird light to a third liquid crystal display element installed in thevicinity, wherein the light output from the third liquid crystal displayelement is input to the color combining means to combine the first lightand second light.
 9. An image display device comprising: a colorseparating means for separating light converged in the polarizationdirection, a first reflecting means to change the optical axis of afirst light and a second light separated in the color separating meansto an approximate right angle; a designated wavelength converter elementto convert the light reflected from the first reflecting means to thepolarization direction of the first light, and permeate the second lightthrough without changing the polarization direction; a colorseparating/combining means to separate the first light and second lightthat permeated the designated wavelength converter element, input thelight to a first and second liquid crystal display element installed atapproximate right angles, combine the first light and second lightreflected from the first liquid crystal display element and secondliquid crystal display element, and emit a light output at anapproximate right angle to the optical axis of the input light; adesignated wavelength converter element to convert the light to a firstlight polarization direction from among the first and second lightemitted from the color combining/separating means; a color combiningmeans to be input with a first light permeated through the designatedwavelength converter element and an input second light; a polarityconverter element to convert the polarization direction of a third lightseparated by the color conversion means; and a means to input a thirdlight, which permeates through the polarity conversion element topermeate the color conversion means, to a third liquid crystal displayelement installed in the vicinity, wherein the third light reflectedfrom the third liquid crystal display element is input to a colorcombining means, and the first and second light is combined and output.10. An image display device according to claim 9, wherein anotherreflecting means is installed, a third light permeating the colorcombining means is reflected by another reflecting means and input to athird liquid crystal display means, and the third light reflected by thethird liquid crystal display element is further reflected by anotherreflecting means and input to the color combining means.
 11. An imagedisplay device according to claim 9, wherein the color separating meansreflects the R light and G light and allows B light to permeate through.12. An image display device according to claim 9, wherein the colorseparating means is a dichroic mirror or a dichroic prism.
 13. An imagedisplay device according to claim 9, wherein the color separating meansand the color combining means are polarized beam splitters.
 14. An imagedisplay device according to claim 8, wherein a designated wavelengthconverter element is installed between the color separating means andthe color separating/combining means.
 15. An image display deviceaccording to claim 8, wherein a designated wavelength converter elementis installed respectively between the color separating means and thecolor separating/combining means, and also between the colorseparating/combining means and the color combining means.
 16. An imagedisplay device according to claim 13, wherein a polarizing plate and apolarity converter element are installed between the color separatingmeans and the color separating/combining means, and also between thecolor separating/combining means and the color combining means.
 17. Animage display device according to claim 9, wherein a colorseparating/combining means for bringing out certain characteristics inlight input to the color separating/combining means is a polarized beamsplitter.
 18. An image display device according to claim 9, wherein acolor separating/combining means and a color combining means are colorseparation and light analyzing elements.
 19. An image display deviceaccording to claim 9, wherein the surface area of the section for thecolor separating/combining means to output light is smaller than thesurface area of the section for the color combining means to be inputwith light.
 20. An image display device according to claim 9, whereinthe color combining means combines the two-colored P polarized lightinput, and the one-colored light S polarized light input at mutuallyintersecting directions, and outputs three-colored light on the opticalaxis direction of the P polarized light.
 21. An image display deviceaccording to claim 18, wherein a projection means is installed forinputting light from the color combining means, and the output axis ofthe color combining means and the optical axis of the projection meansare shifted.
 22. An image display device according to claim 10, whereinthe color combining means is comprised of a prism and the totalreflecting prism constituting the reflecting means is bonded to thecolor combining means.
 23. An image display device comprising a colorseparating means to separate light into a first light and a second lightand a third light, a color separating/combining means to separate andcombine the first light and the second light, first and second liquidcrystal display elements installed at approximate right angles in thevicinity of the color separating/combining means, a third liquid crystaldisplay element to input the third light, and color combining means torespectively combine the first, the second and the third light separatedby the color separating means, wherein the first and second lightseparated by the color separating means to be separated by the colorseparating/combining means are respectively input to the first andsecond liquid crystal display elements, and the first light and secondlight output from the first liquid crystal display element and thesecond liquid crystal display element are combined in the colorcombining/separating means and changed to an optical axis at anapproximate right angle to the input angle, and the first and the secondlight output from the color combining/separating means are input to thecolor combining means by the first reflecting means, and the third lightseparated by the color separating means is reflected by the reflectingmeans and input to the third liquid crystal element, the light outputfrom the third liquid crystal element permeates through the colorseparating means and is input to the color combining means, and thefirst light, second light and third light are combined.
 24. An imagedisplay device according to claim 23, wherein the color separating meansis comprised of prisms, and the reflecting means is a dichroic prism orfull reflecting prism.
 25. An image display device according to claim24, wherein the prisms are aligned with each other.
 26. An image displaydevice according to claim 23, wherein a condenser lens is installed inparallel with an optical axis of a chief ray at the incident side of thecolor combining means and incident side of the colorcombining/separating means, or alternatively a first condenser lens isinstalled between the color separating means and the colorseparating/combining means, and a second condenser lens is installedbetween the color separating means and the color combining means.
 27. Animage display device according to claim 23, wherein a colorseparating/combining means and the color combining means are comprisedof prisms, or the color separating means, the color combining/separatingmeans and the color combining means are comprised of prisms, and a firstcolor alignment film is installed on any of the prism surfaces on theoptical axis of the first light and second light, and a second coloralignment film is installed on any of the prism surfaces on the opticalaxis of the third light.
 28. An image display device according to claim23, wherein a designated wavelength converter element is installed on atleast one of the optical paths of the first and second light and theoptical path of the third light, and color alignment is performed bymeans of the color alignment film and the designated wavelengthconverter element.
 29. An image display device according to claim 23,wherein a designated wavelength converter element is installed on atleast one optical path of an optical path to pass light from the colorseparating/combining means, and an optical path not passing light fromthe color separating/combining means, and color alignment is performedby the color separating means and the designated wavelength converterelement.
 30. An image display device according to claim 23, wherein anyof the color separating means, and the color separating/combining meansare comprised of prisms, and at least one of the polarizing palate andthe designated wavelength converter elements installed in vicinity tothe prisms, are aligned against the prisms.
 31. An image display deviceaccording to claim 23, wherein the color separating means is comprisedof any of a dichroic mirror and a dichroic prism, and a color alignmentfilm is installed in vicinity to the input surface of the colorcombining means, and the color alignment film installed near the colorcombining means and the color separating means are set at halfwavelengths of different values, to improve the color purity.
 32. Animage display device according to claim 23, wherein the color separatingmeans or the color combining means use polarized beam splitters ordichroic prisms comprised of prisms, and the glass material is changedaccording to the application of the prism.
 33. An image display deviceaccording to claim 23, wherein the color separating means and the colorseparating/combining means are comprised of an analyzing polarized beamsplitter, or the color combining means is constituted of prisms formedof a polarized beam splitter or dichroic prism, and the glass materialof the analyzing polarized beam splitter and prism can be changedaccording to the application, and the volume of the prisms is madelarger than the volume of the analyzing polarized beam splitter.
 34. Animage display device according to claim 23, comprising prisms consistingof polarized beam splitters and dichroic prisms in the color separatingmeans or the color separating/combining means, and the liquid crystaldisplay has a frame filled with liquid crystal and a liquid crystalcover glass, wherein an alignment plate is bonded to the first or secondprism comprised of a polarized beam splitter or dichroic prism, and theliquid crystal display element is bonded to the alignment plate.
 35. Animage display device according to claim 23, comprising prisms consistingof polarized beam splitters and dichroic prisms in the color separatingmeans or the color separating/combining means, and the prisms arecomprised of a first prism piece and a second prism piece alignedtogether, and the height of the first prism piece is shorter than theheight of the second prism piece, and a plurality of prisms arecomprised of a first prism piece and a second prism piece alignedtogether and formed so that a step is formed between the first prismpiece and the second prism piece, wherein positioning between aplurality prisms is carried out by utilizing the steps.
 36. An imagedisplay device according to claim 39, wherein a plurality of assemblybase pieces are installed between a first stand mounted with a firstprism piece and a second stand mounted with a second prism piece, and aplurality of prisms are installed in the assembly base pieces.
 37. Animage display device according to claim 23, wherein the G light input tothe color combining means is S polarized light, the R and B light is Ppolarized light, and the optical axis output of the image displayelement to modulate the G light, and the output optical axis of thecolor combining means are at approximate right angles.
 38. An imagedisplay device according to claim 23, wherein the G light input to thecolor combining means is P polarized light, the R and B light is Spolarized light, and the optical axis output of the image displayelement to modulate the G light, and the output optical axis of thecolor combining means are in parallel.
 39. An image display deviceaccording to claim 23, wherein light input to the colorseparating/combining means is separated into a first light and a secondlight and the respective first light and the second light arerespectively input to a first and a second image display element, andthe optical axis of the first and second light obtained from the firstand a second image display elements output from the colorseparating/combining means are input at an approximate right angle tothe optical axis input to the color separating/combining means, and theoutput light optical axis of the separating/combining means is inparallel with the optical axis of the projection means.
 40. An imagedisplay device according to claim 23, comprising a projection means andan optical conversion means, and the color separating/combining unit iscomprised of a color separating means, an image display means, wherein acolor combining means, and configures so that the optical axis of thelight input to color separating/combining unit is in parallel with theoptical axis of light output from the color separating/combining unit,and the light output from the color separating/combining optical unit isconverted to an optical axis in an optical axis conversion means andinput to the projection means.
 41. An image display device comprising,reflective image display elements for forming optical images accordingto video signals from light output from a light source unit, an opticalsystem to beam light onto the reflective image display elements, and aprojection means to project the light output from the reflective imagedisplay elements, wherein two polarity separating/combining means forconverting the polarization of the light, and two colorseparating/combining means for reflecting or permeating light of adesignated wavelength are combined, or three polarityseparating/combining means and one color separating/combining means arecombined on the optical axis of the reflective image display elements.42. An image display device according to claim 41, wherein, to the RGBof the reflective image elements, two polarity separating/combiningmeans and two polarity separating/combining means are combined on theinput/output light optical axis for the three color reflective imagedisplay elements; and another polarized light separating/combining meansor one color separating means are combined at positions just upstreamfor input of light to the two polarity separating/combining means; andfurther one color combining means is installed on the output lightpermeating section of the reflective image display elements.
 43. Animage display device according to claim 42, comprising a structure inwhich two polarity separating/combining means and two colorseparating/combining means are combined on the input/output lightoptical axis of the reflective image display elements; or a structure inwhich three polarity separating/combining means and one colorseparating/combining means are combined, and designated wavelengthconverter elements are installed for converting polarity of light of adesignated wavelength to a polarization direction of a specified angle.44. An image display device comprising, image display elements forforming optical images according to video signals from light output froma light source unit, and an optical system to beam light onto the imagedisplay elements, and a projection means to project the light outputfrom the image display elements onto a screen, wherein the device isinstalled with a polarity separating/combining means to polarize thelight input to the image display elements and also analyze thereflection light of which polarization is converted by the image displayelements, and a color separating means to separate the light output fromthe optical display unit into green, red and blue, and designatedwavelength converter elements are installed to convert only the light ofthe designated wavelength positioned upstream or downstream of thepolarity separating/combining means along the optical path of theseparated red and blue colored light.
 45. An image display device toinput light output from the light source of the optical system to threereflective liquid crystal display elements by way of a colorseparating/combining means for separating the three primary colors red,green and blue, and after combining the three color image lightreflected by the three reflective liquid crystal display elements intocolor image light, to project an enlarged image with a projection lens,wherein the color separating/combining means and color combining meansare a polarized beam splitter, and the color separating means iscomprised of dichroic optical elements having a dichroic reflective thinfilm, or the color separating/combining means is a polarized beamsplitter prism, and the color separating means and the color combiningmeans are a dichroic optical element having a dichroic reflective thinfilm.
 46. An image display device according to claim 45, wherein of thethree reflective liquid crystal display elements, one beam splitterprism is positioned just upstream of the reflective surface of thereflective liquid crystal display element corresponding to the G color,and two reflective liquid crystal display elements corresponding to theR and B light are arrayed to adjoin each other and also forming a 90degree angle, and one beam splitter prism is positioned just upstream ofboth reflecting surfaces.
 47. An image display device according to claim46, wherein the image light output from the two beam splitter prisms areinput and combined by the third beam splitter or the two surfaces of thedichroic optical element.
 48. An image display device according to claim47, wherein the polarization direction of the G light input to thecombining polarized beam splitters or the dichroic optical element forcombining the G image light and the R, B image light is at anapproximate right angle to the polarization direction of the R, B light.49. An image display device according to claim 45, comprising adesignated wavelength converter element to rotate the polarity of lighton a designated wavelength on an optical path passing two colors ofimage light from three primary color image light in the color combiningoptical system.
 50. An image display device to input light output fromthe light source of the optical system to three reflective liquidcrystal display elements by way of a color separating/combining meansfor separating the three primary colors red, green and blue, and aftercombining the three color image light reflected by the three reflectiveliquid crystal display elements into color image light, to project anenlarged image with a projection lens, wherein the image display deviceis installed with a designated wavelength polarized rotator element torotate the polarity of either of the R or the B light an approximateninety degrees to rotate the polarization direction of light for adesignated wavelength on respective optical paths for passing R and Blight separated from the G light.
 51. An image display device accordingto claim 50, wherein the designated wavelength converter elements arecomprised of a first and a second designated wavelength converterelement; and when separating colors, after separating the G light, the Rand B light are separated utilizing the first designated wavelengthconverter element and the polarized beam splitter prism; and whencombining colors, after combining the R and B light utilizing thepolarized beam splitter prism, the second designated wavelengthconverter element is utilized to convert it to approximately samepolarization direction to each other and then combine the G light. 52.An image display device according to claim 49, wherein the designatedwavelength converter element (wavelength selectable polarity rotatorelement) rotates the polarization to a wavelength range in the vicinityof 400 nm to 500 nm, or to a wavelength range in the vicinity of 600 nmto 700 nm.
 53. An image display device according to claim 52, whereinthe polarized beam splitter prism and the designated wavelengthconverter element are mutually aligned together into an integratedshape, or the polarized beam splitter prism and the designatedwavelength converter element and a dichroic prism as the dichroicoptical element are mutually aligned together into an integrated shape.54. An image display device according to claim 51, wherein afterseparation of the G light, polarity rectifier elements such aspolarizing plates are respectively installed upstream of the polarizedbeam splitter prism in the optical path passing the G light as well asthe optical path passing the R and B light.
 55. An image display deviceaccording to claim 54, wherein a polarizing plate is installed in thevicinity of any of a color separating means, a colorseparating/combining means, and a color combining means, and one surfaceof a glass plate is attached to the polarizing plate, and a coloralignment film is formed on the other surface of the glass plate; or adesignated wave length converter element is installed in the vicinity ofany of a color separating means, a color separating/combining means, anda color combining means, and one surface of a glass plate is attached tothe designated wavelength converter element, and a color alignment filmis formed on the other surface of the glass plate.
 56. An image displaydevice according to claim 55, comprising a color separating means toseparate a first light, a second light, and a third light, a first prismto lead the first light into a first image display element, a secondprism to lead the second light and third light into a second and a thirdimage display element, and a color combining means to combine the firstlight, second light and third light, wherein a first color alignmentfilm is formed on one or both sides of a first prism for input andoutput of the first light, and a second color alignment film is formedon one or either or both sides of the surfaces for input and output ofthe second and third lights.
 57. An image display device according toclaim 56, wherein a first color alignment film is formed on a firstprism surface for input and output of a first light and on any one orboth surfaces of a third prism for input of a first light; and a secondcolor alignment film is formed on a second prism surface for input andoutput of a second light and a third light; and on any one or bothsurfaces of a third prism for input of a second light and a third light.58. An image display device according to claim 57, wherein a designatedwavelength converter element is installed on at least one of opticalpaths for an optical path of a first light and an optical path of asecond light, and color alignment is performed by means of the coloralignment film and the designated wavelength converter element.
 59. Animage display device according to claim 58, comprising a colorseparating means to separate a first light, a second and a third light,a first polarized beam splitter to input a first light to an imagedisplay element and analyze light, a second polarized beam splitter toinput a second and a third light respectively to a second and a thirdimage display element and analyze the light, a color combining means tocombine the first through the third light, and a designated wavelengthconverter element installed on at least one of the light paths of theoptical path for the first light and optical path for the second andthird lights, wherein color alignment is performed by means of the colorseparating means and the designated wavelength converter element.
 60. Animage display device according to claim 59, wherein a combination of thehalf value of the color separator means and the half value of the firstand second designated wavelength converter elements, cut out the lightin the vicinity of 500 nm or in the vicinity of 580 nm or in thevicinity of both wavelengths.
 61. An image display device according toclaim 58, wherein an optical unit for modulating the light separated bythe color separating means with an image display element and combiningthe light with the color combining means and outputting the light withan output means, is comprised of a color separating means consisting ofeither of a dichroic mirror or dichroic prism, and comprised of colorcombining means consisting of either of a dichroic mirror or dichroicprism, and different values are set for the half-wavelength of the colorseparator means and the half wavelength of the color combining means, toimprove the color purity.
 62. An image display device according to claim54, wherein in the optical unit, the color separation and combination ofthe two colors of R light and B light are performed by one polarizedbeam splitter, and further, a polarizing plate for light only of adesignated wavelength functions as a polarity rectifier element forlight of a designated wavelength and is installed between the lightsource and the image light input surface of the polarized beam splitterprism.
 63. An image display device according to claim 53, wherein apolarity rectifier element is installed in front or behind the polarityseparating/combining element on either of the optical path of the greenlight or the optical path of the red light after separation of at leastthe green light, and the polarity rectifier element is installed infront of the designated wavelength converter element for convertingpolarized light only for a designated wavelength.
 64. An image displaydevice according to claim 53, wherein a designated wavelength converterelement for converting the polarization direction of light only on adesignated wavelength, and a designated wavelength converter elementhaving a color combining means for combining, green, red and blue lightand inputting it to a projection means, rotates the polarizationdirection of either the red or the blue light approximate ninetydegrees, and when S polarized light, is converted to P polarized light,and when P polarized light is converted to S polarized light, and whenthe red and the blue light is reflected and input to projection lens,the P polarized light of the red and the blue light is converted to Spolarized light, and when the red and the blue light permeates the colorcombining means and is input to the projector lens, the S polarizedlight of the red light and blue light is converted to P polarized light.65. An image display device according to claim 63, wherein a cooling airpassage is installed between a polarized beam splitter and at least apolarizing plate or a designated wavelength converter element; or acoolant medium is distributed in the vicinity of the color separatingmeans and color combining means.
 66. An image display device accordingto claim 65, wherein a condenser lens is installed between the lightsource and the polarized beam splitter, and the chief ray of the lightinput to the polarized beam splitter prism is input at an approximateright angle to the sides of the reflective liquid crystal displayelement.
 67. An image display device according to claim 66, wherein acondenser lens is installed on the optical path on the incident side ofthe color separating means, and the chief ray of the light input to thepolarized beam splitter prism is input in parallel with the prism, andinput at an approximate right angle to the liquid crystal displayelement.
 68. An image display device according to claim 67, wherein apolarizing plate or a dichroic filter is installed on the flat surfaceof the condenser lens.
 69. An image display device according to claim68, wherein condenser lenses are installed just in front of therespective reflective liquid crystal display elements, and the chief rayfor light input to the reflective liquid crystal display elements isinput at an approximate right angle to the sides of the reflectiveliquid crystal display elements, and the first composite focus pointposition of a lens group after the condenser lens is positioned in thevicinity of the surface of the aperture of the projection lens.
 70. Animage display device according to claim 69, wherein the center axis ofthe condenser lens nearly matches the center axis of the reflectiveliquid crystal display element, and is center-offset to the center axisof the projection lens.
 71. An image display device according to claim69, wherein the sloping thin dichroic film of the dichroic opticalelement changes according to the input angle of the light, and the filmthickness changes in a fixed direction thereby to change the filmwavelength characteristics.
 72. An image display device according toclaim 71, wherein the size of a prism for combining the G image lightand the R, B image light, is larger than the polarized beam splitterprism installed just in front of the R, B reflective liquid crystaldisplay element, and larger than the polarized beam splitter prisminstalled just in front of the G reflective liquid crystal displayelement.
 73. An image display device according to claim 72, wherein atleast one of the color separating/combining means is a dichroic prism,and a chamfering section is installed at one corner side larger than theother corner side in a direction perpendicular to the optical axis ofthe color separating means, and a structural member or another opticalmember is installed in the chamfering section.
 74. An image displaydevice according to claim 73, wherein both the upper and lower surfacesof the prisms are painted black.